Energy Conservation and Emission Reduction Strategies


TDM Encyclopedia

Victoria Transport Policy Institute


Updated 6 September 2019

This chapter identifies and evaluates various strategies to reduce transport energy consumption and pollution emissions. These include Transportation Demand Management strategies that affect travel behavior; incentives for more efficient and less polluting vehicles; alternative fuels; methods to identify, repair and scrap high-emitting vehicles; regulations; pricing and information programs. It discusses ways to evaluate and compare these strategies and recommends best practices.




Introduction. 2

Factors Affecting Vehicle Energy Consumption, Emissions and Exposure. 5

Comparing Clean Vehicle and TDM Strategies. 12

Demand Management Strategies. 15

Distance-Based Emission Fees. 15

Fuel Tax Increases. 16

Freight Transport Management 18

Aviation Transport Management 19

TDM Programs. 20

Pay-As-You-Drive Vehicle Insurance and Other Distance Based Fees. 21

Market Reforms. 21

Land Use Management Strategies. 22

Nonmotorized Transportation Improvements and Encouragement 24

Ridesharing. 24

Road Pricing. 25

Transit Improvements and Incentives. 25

High Occupant Vehicle (HOV) Priority. 26

Parking Management and Parking Pricing. 27

TDM Marketing. 27

Traffic Calming and Roundabouts. 27

Car-Free Planning and Vehicle Restrictions. 28

Telework. 28

Speed Reductions. 28

Sustainable Transportation Planning. 29

Other Strategies. 29

Promote Efficient and Low Emission Vehicle Purchases. 29

Emission Standards. 29

Fuel Efficiency Standards. 30

Gas Guzzler Taxes. 30

Feebates. 31

Close Gas Guzzler Loopholes. 31

Efficiency-Based Annual Registration Fees. 31

Transit Emission Reduction Programs. 32

Motorcycle Encouragement 32

Super-Efficient and Alternative Fuel Vehicle Incentives. 32

Low and Zero Emission Vehicle Mandates. 32

Inspection and Maintenance (I/M) Programs. 33

Roadside “High Emitter” Identification. 33

Scrapage Programs. 33

Fuel Quality Improvements. 34

Emission Capping and Trading. 34

Fleet Management and Driver Training. 34

Anti-Idling. 35

Neighborhood Vehicles. 35

Resurface Highways. 36

Summary of Emission Reduction Strategies. 36

Policy Reforms and Incentives. 36

Congestion-Reduction Strategies. 37

Flextime. 39

Road Capacity Expansion and Traffic Signal Synchronization. 39

Intelligent Transportation Systems. 40

Evaluating Energy Conservation and Emission Reduction Strategies. 40

Efficient Vehicles Versus Efficient Transportation. 43

Best Practices. 44

Examples and Case Studies. 45

Vacaville Becomes Voltageville With Electric Vehicle Implementation. 45

Minimize the Air Pollution from Your Consumer Choices with ( 45

0800 SMOKEY. 46

Other Cities Follow Lead of New York Buses, Without Choking. 46

Trees for Travel ( 48

Emission Prices Are More Efficient than Emission Caps. 48

Texas Remote Sensing Emission Enforcement ( 50

Seattle Climate Action Plan ( 52

Visioning and Backcasting for UK Transport Policy ( 53

Emission Reductions in Developing Countries ( 53

Emission Reduction Legislation and Strategies (ETAAC, 2008) 53

Urban Transportation Emissions Calculator ( 54

Emission Calculators. 56

Emission Reduction Legislation (Committee on Energy and Commerce, 2008) 59

References And Resources For More Information. 60




Motor vehicles are major energy consumers and sources of air, noise and water pollution. Transportation represents about 27% of total U.S. energy consumption and 70% of total petroleum consumption (ORNL, 2001). Transportation energy consumed by mode is summarized below. Personal transportation represents about 60%, and commercial transport about 40%, of total transportation energy consumption.


Table 1            Vehicle Energy Use (ORNL, 2001, Table 2.5)


Trillion BTUs

Percent of Total




Light Trucks (including vans and SUVs)



Trucks & Private Buses












Off-highway (construction and agriculture)














Detailed information on vehicle energy consumption and emissions is available from:

·         Comparison of Energy Use & CO2 Emissions From Different Transportation Modes (

·         GHG Assessment Tools ( describes various methods used to quantify transport sector greenhouse gas emissions, and the impacts of emission reduction strategies.

·         Transportation Cost and Benefit Analysis Guidebook (, includes chapters on air, noise and water pollution, and resource consumption external costs.

·         Transportation Air Quality Center, USEPA ( provides information on vehicle emissions and emission reduction strategies.

·         Transportation Energy Data Book, ORNL ( provides information on U.S. vehicle energy consumption and emissions.

·         Annual Energy Review, Energy Information Administration ( provides information on energy production, consumption and prices.

·         TC (2009), The Urban Transportation Emissions Calculator ( is a user-friendly, Internet-based tool developed by Transport Canada that estimates greenhouse gas and criteria air contaminant emissions from urban transportation. It can be used in a wide variety of contexts involving different vehicle types (e.g., cars, commercial trucks, buses, light rail), fuel technologies (e.g., gasoline, diesel, hybrid, ethanol, biodiesel, etc.), and planning horizons (2006-2031).

·         European Environment Agency ( provides international information on vehicle energy consumption and emissions.

·         Office of Transportation And Air Quality Modeling Tools, USEPA ( has tools for evaluating the emission reduction impacts of TDM strategies.

·         The Green Vehicle Guide, USEPA ( reports emissions and fuel consumption rates per vehicle mile for specific model years.

·         For My World Tailpipe Tally ( provides motor vehicle fuel consumption, fuel cost and pollution emissions for specific model-years.

·         The USEPA Greenhouse Gas Equivalencies Calculator ( provides information that compares various units and examples of climate change emissions and emission reduction impacts.

·         USEPA Transportation Tools ( provides links to sources of information on transportation activities, emissions and emission reduction strategies. 

·         The Climate Change Cost Calculator ( allows users to estimate a person’s air pollution emissions and how these can be changed.

·         “Air Pollution Costs,” Online TDM Encyclopedia, Victoria Transport Policy Institute (, 2002.

·         The Zerofootprint Calculator ( enables you to measure and understand the impact of your ecological footprint, taking into account both direct and indirect resource consumption. Zerofootprint Cities is an initiative designed for Mayors of the world's cities to engage their citizens around climate change.



Major vehicle pollutants and their harmful effects are summarized in Table 2 (for more detailed information see appropriate chapters in the Transportation Cost and Benefit Analysis Guidebook at Some of these impacts are local in nature, so where emissions occur affects the damages they impose, while other are regional or global, and so where they are released is less important.


Table 2            Vehicle Pollution Emissions (Litman 2009)




Harmful Effects


Carbon monoxide (CO)

A toxic gas, undermines blood’s ability to carry oxygen.


Human health, Climate change

Very local

Fine particulates (PM10; PM2.5)

Inhaleable particles consisting of bits of fuel and carbon.

Diesel engines and other sources.

Human health, aesthetics.

Local and Regional

Road dust

Dust particles created by vehicle movement.

Vehicle use.

Human health, aesthetics


Nitrogen oxides (NOx)

A variety of compounds, some of which are toxic, and all of which contribute to ozone.


Human health, ozone precursor.


Hydrocarbons (HC)

Unburned fuel. Forms ozone.

Fuel production and engines.

Human health, ozone precursor.


Volatile organic hydrocarbons (VOC).

A variety of organic compounds that form aerosols.

Fuel production and engines.

Human health, ozone precursor.

Local and Regional

Toxics (e.g. benzene)

VOCs that are toxic and carcinogenic.

Fuel production and engines.

Human health risks

Very local

Ozone (O2)

Major urban air pollution problem resulting from NOx and VOCs combined in sunlight.

NOx and VOC

Human health, plants, aesthetics.


Sulfur oxides (SOx)

Lung irritant, and causes acid rain.

Diesel engines

Human health risks, acid rain


Carbon dioxide (CO2)

A byproduct of combustion.

Fuel production and engines.

Climate change


Methane (CH4)

A gas with significant greenhouse gas properties.

Fuel production and engines.

Climate change



Durable chemical widely used for industrial purposes, now banned due to environmental risks.

Vehicle (especially older air conditioners).

Ozone depletion


Noise pollution

Undesirable noise produced by vehicles.

Engine, tires, wind

Aesthetic, distraction, reduced property values.


Water pollution

Water pollution caused by motor vehicles.

Leaking liquids

Human health, ecological.

Local and Regional

This table summarizes various types of motor vehicle pollution emissions and their impacts.



Although tailpipe emissions tend to receive the most attention, pollution is also produced during fuel production and distribution (called “upstream” emissions), vehicle refueling, hot soak (i.e., evaporative emissions that occur after an engine is turned off), and mechanical emissions produced from road dust and wear of brake linings and tires. More than half of some types of emissions occur during cold-start and hot soak conditions, and so are affected more by the number of vehicle trips that occur than by mileage. For example, increasing trip length from 10 to 20 miles increases mileage by 100%, but only increases some types of emissions by 35%.


Vehicle pollution and energy consumption impose a variety of health, economic and environmental costs on society (Transportation Costs). Several studies have investigated these costs, and some include monetized estimates (USEPA 1999; Litman 2009; Stern 2006). Delucchi (2000) estimates that U.S. motor vehicle air and noise pollution costs total approximately $100 billion annually.



Factors Affecting Vehicle Energy Consumption, Emissions and Exposure

Several factors described below affect vehicle energy consumption and emission rates, human exposure to harmful emissions, and the costs they impose. Various models, such as URBEMIS ( can be used to predict the emission reduction effects of various mobility management and smart growth strategies (Nelson/Nygaard 2005; Mehaffy, Cowan and Urge-Vorsatz 2009; Mehaffy 2015). The USDOT’s Center for Climate Change and Environmental Forecasting ( provides emission inventory data (the emissions produced by various sectors). Grant, Choate and Pederson (2008) summarize various models that can be used to predict transportation emissions and the effectiveness of various emission reduction strategies.



Land Use Patterns

Land Use Patterns affect the amount and type of travel that occurs in an area. People who live and work in more compact, mixed, multi-modal communities tend to drive less and rely more on alternative forms of transportation, and so consume less energy and produce less pollution per capita (Sierra Club 2005; Lawrence Frank and Company 2005)



Travel Mode and Vehicle Type

Table 3 summarizes the energy consumption rates of various travel modes and vehicle types. Since the US fleet of personal vehicles averages about 19.5 miles-per-gallon, and a gallon of gasoline consumed produces 19.6 pounds of CO2, an average vehicle-mile produces about one pound of CO2 (or a quarter of a kilograms per vehicle-kilometer).


Fuel consumption and emission rates per passenger-mile depend on load factors: A bus with 50 passengers uses about one-tenth the energy per passenger-mile as an average automobile, but in the U.S., energy consumption per passenger-mile is little higher for transit systems than for driving, due to low load factors. In other countries, and in U.S. cities with higher levels of transit demand, transit is much more energy efficient than driving. Increasing ridership using existing vehicle capacity consumes little additional energy and produces little additional pollution, so the marginal cost of an additional rider in a motor vehicle (i.e., a Rideshare passenger) can be very low.


Table 3            Average Fuel Consumption 2001 (BTS, Tables 1-29, 4-20, 4-23, 4-24; APTA, 2002)

Vehicle Class

Average MPG


BTU/Pass. Mile

Passenger Cars




Vans, Pickup Trucks, SUVs


Vans, Pickup Trucks, SUVs






Single Unit Truck


Transit, Bus


Combination Truck


Transit, Electric Light Rail


Buses (all types)


Intercity Rail, diesel


This table summarizes average fuel consumption per vehicle, and energy consumption per passenger-mile for various vehicle types.



A significant amount of energy is used to produce vehicles, called embodied energy. The table below estimates total energy for various travel modes, including both the energy embodied in the vehicle and the fuel used in vehicle operation.


Table 4          Energy Use By Mode (MJ/Passenger km) (Lenzen, 1999)









Light Rail
















Heavy Rail




Car, Petrol




Car, Diesel




Car, LPG




Private Bus
















Private Air




Carter Air




Regional Air




Domestic Air




International Air






Vehicle Design – Drive Train Efficiency

Energy consumption and emission rates vary significantly due to vehicle design. Drive system design improvements have significantly increased vehicle fuel efficiency, but in recent years consumers have used this increased efficiency to purchase larger, heavier, more powerful vehicles rather than reducing their fuel consumption.


It is common to hear claims that automobile emissions have declined by 90% or more over the last few decades, but this is an exaggeration. Engine and fuel improvements have significantly reduced tailpipe emission rates under design conditions, but a large portion of driving occurs under non-design conditions and non-tailpipe emissions such as tire particulates and road dust are not controlled by these technologies.


Some studies predict that per-mile energy consumption and emission rates could be reduced 30-50% by fully implementing cost-effective vehicle design improvements using available technologies, without significantly changing performance (Greene and DeCicco 2000), although most researchers consider a 25% reduction more realistic (OECD/IEA, 2001), and this requires that average vehicle size, weight and acceleration not increase. Even modest shifts in vehicle type, for example from a large to a medium-size SUV, or by reducing vehicle weight by a few hundred pounds, can provide significant energy conservation benefits if widely implemented. Greater energy savings and emission reductions are possible by shifting to small, super-efficient vehicles (, as indicated in Table 5. But consumers currently have little incentive to choose efficient vehicles due to relatively low fuel prices.


Table 5            Fuel Consumption Comparison (Liters Per 100 Kilometers)


Drive System





Average SUV






Average Car






Toyota Prius






Honda Insight






Lupo 3L


2 or 4




Currently available high-efficiency production vehicles consume less than half the fuel used by conventional automobiles, and less than a third as much as an average SUV.



It is uncertain how much increased fuel efficiency reduces emissions other than CO2. Manufactures design vehicles to meet specific emission standards, and so apply more emission reduction strategies in vehicles with larger engines than in vehicles with smaller engines. Some emission control strategies reduce fuel efficiency (for example, catalysts add weight, and tuning engines to minimize NOx emissions increases fuel consumption). Lighter, aerodynamic vehicles tend to emit less non-tailpipe emissions such as tire particles and road dust, but these effects are difficult to quantify. Most emissions decline in proportional to mileage.



Operating Conditions

Vehicle traffic speed and load affects emission rates. Modern vehicles maintain maximum efficiency in a broad range from about 30 to 60 miles per hour, as illustrated in Figure 1. Fuel efficiency declines at higher and lower speeds.


Figure 1          Vehicle Fuel Efficiency By Speed (ORNL, 2000, Table 7.21)

This figure shows how average vehicle fuel efficiency for a typical set of automobiles (cars, SUVs and light trucks) is affected by vehicle speed.



Per-mile emissions of CO and VOCs also tend to be minimized from about 30 to 60 mph, and increase at higher and lower speeds, but NOx emissions are minimized at 30 mph, and increase with vehicle speeds, as illustrated in Figure 2.


Figure 2          Vehicle Emissions By Speed (TRB 1995)

This figure shows how typical vehicle emissions are affected by speed. Emissions tend to increase at very low and very high speeds.



Fuel consumption and pollutant emission rates (per vehicle-mile) are much higher for the first few miles of driving, when engines are cold (called cold starts). Older vehicles that lack current emission controls and vehicles with engines that are poorly tuned tend to have very high emissions rates (called super emitters), often more than 10 times greater than the fleet average.



Fuel Type

A variety of fuels other than gasoline can power automobiles, including diesel, synthetic gasoline, compressed natural gas (CNG), methanol, ethanol, battery electric, and hydrogen. Table 5 summarizes advantages and disadvantages of different fuels. For detailed information see the U.S. Department of Energy’s Alternative Fuels Data Center (, the Clean Cities website (, and the Centre for Alternative Transportation Fuels ( The US Department of Energy’s Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model ( calculated the lifecycle emission impacts of alternative fuels (also see Delucchi, 2003).


Table 6            Alternative Fuels Compared (Alternative Fuels Data Center; Pickrell)







Widely available and used. Reduces carbon emissions.

Increases emissions of particulates, sulfur and noise.



Increased efficiency and reduced emissions.

Requires rebuilding engines. Limited availability.



Increased efficiency and reduced emissions.

Requires rebuilding engines. Limited availability. May reduce methane.



Reduces some emissions.

Poisonous. Increases some emissions.



Reduces some emissions.

Increases some emissions. Energy savings depend on fuel source.



No tailpipe emissions. May be generated from renewable sources.

Reduced vehicle performance. Vehicles are currently expensive. Energy savings depend on how electricity is generated.



No tailpipe pollutants.

Not currently available. Energy savings depend on how hydrogen is produced.

* Estimated reduction in lifecycle CO2 emissions per vehicle-mile compared with gasoline.



Alternative fuels tend to reduce some types of emissions, but in most cases their total benefits (including “upstream” emissions during production and distribution) are modest, and many increase some types of harmful emissions (Koplow 2006; Bourne 2007). For example, current diesel engines reduce CO2 emissions but increase sulphur dioxide, particulate matter, and noise compared with a gasoline engine, although these differences are declining due to improved engine design and fuel quality. Emission standards for heavy diesel engines are becoming more stringent, and special programs are retrofitting existing buses with cleaner engines. However, although these engines reduce particulate emissions by weight, they increase the number of very fine particulates (smaller than 1 micron), which are considered most harmful to human health. Some transit systems are converting to alternative fuels, such as CNG. About 15% of current transit bus fuel consumption consists of clean fuels (CNG, LPG or alcohol), and more than 20% of new transit buses purchased are designed to operate on such fuels (APTA).


The energy conservation and emission reduction benefits of some fuels depend on how they are produced. For example, one study concludes that alcohol from cellulosic feedstocks offers the best lifecycle reduction in greenhouse gases, and in some countries could account for as much as a 7.5% of vehicle fuel production, reducing net carbon emissions by as much as 5%, but alcohol produced in other ways provides little benefit, or even increases greenhouse emissions (OECD/IEA, 2001, p. 135). The lifecycle emissions of electric vehicles (including battery-powered cars, electric trolleys and trains) depend on the marginal source of electricity they use: renewable and nuclear generation reduces total emissions, but coal generation tends to increase CO2 and sulphur emissions (Delucchi 2003).




A growing body of research is investigating how pollution exposure affects health, taking into account the distance between emission sources and lungs, and the amount of pollution that people actually inhale, as summarized in the box below.


Air Pollution Exposure Research


Doug Brugge, John L Durant and Christine Rioux (2007), “Near-Highway Pollutants In Motor Vehicle Exhaust: A Review Of Epidemiologic Evidence Of Cardiac And Pulmonary Health Risks,” Environmental Health 6, No 23 (


Community Assessment of Freeway Exposure & Health Study: CAFEH (; also see


Lawrence Frank, Andrew Devlin, Shana Johnstone and Josh van Loon (2010), Neighbourhood Design, Travel, and Health in Metro Vancouver: Using a Walkability Index, Active Transportation Collaboratory (; at


Lawrence D. Frank, et al. (2011), An Assessment of Urban Form and Pedestrian and Transit Improvements as an Integrated GHG Reduction Strategy, Washington State Department of Transportation (; at


Julian D. Marshall, Michael Brauer and Lawrence D. Frank (2009), “Healthy Neighborhoods: Walkability and Air Pollution,” Environmental Health Perspectives, Vol. 117, No. 11, pp. 1752–1759; summary at


NZTA (2011), Determination of Personal Exposure to Traffic Pollution While Travelling by Different Modes, The New Zealand Transport Agency (; at



Air pollution costs (per ton of emission) are higher where population densities are high, Several studies indicate that automobile occupants are exposed to more harmful air pollution than people traveling by other modes, but pedestrians and cyclists inhale more air per minute and so may be exposed to greater risk (NZTA 2011). Some demographic groups, such as children, seniors and people with allergies, are likely to experience more harm from a given level of air pollution exposure.



Emission Reduction Impact Summary

Below are some factors that affect how transportation changes affect energy consumption and pollution emissions.


·         Changes in the number of vehicle trips tend to cause a proportional reduction in energy consumption and emissions.


·         Because emission rates are high during the first few minutes of vehicle operation (i.e., cold starts), reductions in average trip length provide relatively modest pollution emission reductions. For example, reducing average automobile trip lengths from 10 to 8 miles represents a 20% reduction in mileage, but might only provide a 10% reduction in pollution emissions.


·         Reductions in the number of short vehicle trips can provide relatively large pollution emission reductions. For example, shifting 5% of automobile trips to bicycling and walking might reduce total automobile mileage by just 2% (since these are short trips), but emission impacts may decline by 4-8% due to the relatively high emission rates of the vehicle mileage foregone.


·         Older vehicles (greater than 10 years) produce relatively high emissions per mile, although they tend to be driven relatively few miles per year. Programs that reduce driving by older or out-of-tune vehicles may provide relatively large emission reductions.


·         Non-tailpipe emissions such as road dust, brake linings and tire wear are affected by vehicle mileage and weight.


·         Reducing emissions with localized impacts (CO, VOC, NOx, toxics, particulates) in geographic areas with limited air circulation and inversions provides greater benefits than reductions of the same emissions in other areas.


·         Changing from stop-and-go to moderate-speed traffic flow increases fuel efficiency and reduces air pollution emissions, but changing from moderate speeds to high speeds increases some emissions. As a result, strategies that reduce extreme congestion reduce emissions (e.g., Level of Service F changing to C), but strategies that reduce moderate traffic congestion (e.g. LOS C to A) can increase energy consumption and some types of pollution emissions, particularly if it induces additional vehicle mileage.



How Transportation Is Measured Affects Analysis

Which units are used to Measure Transportation can affect energy and emission evaluations. For example, increasing land use density may increase emission rates per acre and per vehicle-mile, because it increases the number of people per acre and results in shorter and more congested vehicle trips, but reduces total vehicle ownership and annual mileage, so emissions decline per vehicle and per capita. Congestion reduction strategies reduce energy consumption and emissions per vehicle-mile, but may increase per capita energy consumption and emissions if they result in increased vehicle mileage, as discussed later in this chapter.



Comparing Clean Vehicle and TDM Strategies

There are two general ways to reduce vehicle air pollution emissions: reduce emission rates per vehicle-kilometre (called Clean Vehicle strategies), or reduce total vehicle travel (called Transportation Demand Management or TDM, or Mobility Management). Table 7 lists common examples of these strategies. One study (Tight, et al. 2007) suggests that feasible, cost-effective strategies could reduce household transportation energy consumption about 40% in the U.K. (and probably much more in the U.S., where per capita transportation energy consumption is much higher), about half due to cleaner vehicles and half due to vehicle travel reductions.


Table 7            Summary of Emission Reduction Strategies

Clean Vehicles (Reduce Emission Rates)

TDM (Reduce Vehicle Travel)


Emission-Based Annual Registration Fees

Emission Standards


Fuel Efficiency Standards

Fuel Quality Improvements

Inspection And Maintenance (I/M) Programs

Low And Zero Emission Vehicle Mandates

Neighborhood Vehicles

Promote The Purchase Of Cleaner Vehicles

Resurface Highways

Roadside “High Emitter” Identification

Scrapage Programs

Super-Efficient And Alternative Fuel Incentives

Transit Emission Reduction Programs

Aviation Transport Management

Car-Free Planning And Vehicle Restrictions

Distance Based Fees

Distance-Based Emission Fees

Freight Transport Management

Fuel Tax Increases

Land Use Management Strategies

Market Reforms

Nonmotorized Transportation

Parking Management And Parking Pricing

Pay-As-You-Drive Vehicle Insurance


Road Pricing

Speed Reductions

TDM Marketing

TDM Programs


Traffic Calming And Roundabouts

Transit Improvements And Incentives

This table identifies various types of emission reduction strategies, including those that reduce emission rates, and those that reduce total vehicle travel.



Range of Benefits

Clean Vehicle and TDM strategies can both reduce transportation energy consumption and emissions, but they differ in important ways. Clean Vehicle strategies tend to provide just one or two types of benefits and impose one or two types of costs. For example, stricter emission control standards reduce emissions, increase vehicle production costs, and sometimes reduce vehicle performance. There are few other impacts to consider.


On the other hand, TDM strategies tend to provide multiple benefits, and may impose multiple costs. For example, parking pricing can help reduce traffic congestion, road and parking facility costs, traffic crashes, and urban sprawl, as well as pollution emissions. It imposes financial costs on motorists, provides revenue to parking facility owners, and adds transaction costs for collecting fees and dealing with violators. From some perspectives it increases equity (i.e., motorists pay directly for what they use), but from others it reduces equity (i.e., if it is regressive).


Table 8            Comparing Strategies (Litman, 2006)

Planning Objective

Efficient and Alternative Fuel Vehicles

TDM Solutions

Congestion Reduction



Parking Cost Savings



Facility Costs Savings



Consumer Costs Savings



Reduced Traffic Accidents



Improved Mobility Options



Energy Conservation



Pollution Reduction



Physical Fitness & Health



Land Use Objectives



Community Livability



Some transport improvement strategies help achieve one or two objectives (+), but by increasing total vehicle travel contradict others (-). TDM strategies reduce total motor vehicle travel, and so support many planning objectives, providing multiple economic, social and environmental benefits.



TDM strategies are often justified based on their economic and social benefits, providing environmental benefits at essentially no additional costs. On the other hand, because of their multiple costs, TDM strategies often face a variety of political and institutional barriers.



Implementation Requirements

Clean Vehicle and TDM strategies also tend to differ in how they are implemented. Clean Vehicle strategies tend to rely on vehicle design changes implemented in response to government regulations or consumer incentives. TDM strategies often involve planning and pricing changes, or special programs implemented at the regional or local level. TDM implementation can involve many stakeholders, and require new institutional relationships and responsibilities. For example, many TDM strategies involve cooperation among various levels of government, businesses, community organizations and individual people. They may require transportation agencies to become involved in new types of programs and services.


Most Clean Vehicle strategies can be implemented individually, and their impacts are relatively easy to predict. TDM strategies tend to be most effective if implemented as part of an integrated program, and their individual impacts may be difficult to quantify. For example, parking pricing tends to be most effective at reducing automobile travel if implemented in conjunction with walking, cycling, ridesharing and transit improvements, and other pricing and land use management strategies.


Various public policies and Institutional Reforms can help implement TDM strategies (Leotta, 2007). The Center for Clean Air Policy identifies the following major categories of TDM implementation policies:



Most individual TDM strategies have modest impacts, affecting a small portion of total vehicle travel, but their impacts are cumulative and synergistic. An integrated TDM program can often reduce 20-30% of automobile travel where it is applied. Some studies suggest that comprehensive implementation of TDM strategies to the degree that they are economically justified could reduce total vehicle travel by more than a third.


Some people are skeptical that TDM strategies are feasible, because they require consumers to change their travel habits, and support policy changes such as pricing reforms. Although such changes may be difficult to implement, there are examples of successes, including recycling, smoking reductions and seat belt use. In each case, a combination of public education, policy changes and support services have had a dramatic impact on behavior patterns, indicating that consumers can support such changes both politically and individually.


Accounting For Vehicle Travel Changes

Most TDM strategies reduce total Vehicle Kilometres Traveled (VKT), while some Clean Vehicle technologies increase VKT. For example, a pricing or land use management strategy might reduce vehicle mileage by 5-10%, while shifts to more fuel-efficient or alternative fuel vehicles may increase total vehicle mileage by the same amount, by reducing per-kilometre vehicle costs. As a result, the TDM strategy will reduce traffic congestion, road and parking facility costs, crashes, urban sprawl and traffic noise, while Clean Vehicles can increase these costs.


It is important to account for these mileage changes when evaluating and comparing emission reduction options (Litman 2005). These mileage-related costs and benefits are generally greater in total value than emission costs, as indicated in Figure 1. A strategy that reduces energy consumption or pollution emissions by 20% but increases mileage-related costs by just 5% may harm society overall. On the other hand, an energy conservation or pollution reduction strategy becomes far more valuable to society if it also reduces mileage-related costs.



Demand Management Strategies

The following TDM strategies tend to be particularly effective at reducing energy consumption and pollution emissions.


Distance-Based Emission Fees

Distance-Based Emission Fees are mileage-based charges that reflect a vehicle’s emission rate. For example, an older vehicle that lacks current emission controls might pay 5¢ per mile, while a newer vehicle might pay 1¢, and an Ultra-Low Emission Vehicle might pay 0.2¢. This gives motorists with higher polluting vehicles a greater incentive to reduce their mileage, and conversely, gives motorists who drive high mileage a greater incentive to choose low polluting vehicles. Fees can vary depending on when and where driving occurs, with higher charges at times and locations where pollution impacts are greater (Pricing Methods). A more advanced system uses electronic sensors to measure actual tailpipe emissions when a vehicle is driven, giving motorists an incentive to minimize emissions in a variety of ways: choosing less polluting vehicles, reducing mileage, keeping engines well-tuned, and driving more smoothly.


Such fees result in relatively large emission reductions and relatively modest mileage reductions. For example, one study predicts that a fee based on measured tailpipe emissions, which averages about 1¢ per vehicle-mile (but higher for more polluting vehicles) would reduce mileage by about 2%, but energy consumption would decline by 7% and air pollution emissions would decline by almost 20%, as indicated in the table below.


Table 9            Impacts of Emission Charges, in Year 2010 (Harvey and Deakin, 1998, Table B.10)


Fee Basis








Vehicle Model







Bay Area

Vehicle Use








Vehicle Model








Vehicle Use








Vehicle Model







San Diego

Vehicle Use








Vehicle Model







South Coast

Vehicle Use







Vehicle Model Fee Basis = a per-mile fee based on vehicle model and year. Vehicle Use Fee Basis = a fee based on measured tailpipe emissions of each individual vehicle, using electronic instrumentation.  VMT = change in total vehicle mileage. Trips = change in total vehicle trips. Delay = change in congestion delay. Fuel = change in fuel consumption. ROG = a criteria air pollutant. Revenue = annual revenue in millions of 1991 U.S. dollars. See original report for additional notes and data.



Fuel Tax Increases and Carbon Taxes

Fuel Taxes are often considered a road user fee, which can be increased to recover more roadway costs. Carbon Taxes are taxes based on fossil fuel carbon content, and therefore a tax on carbon dioxide emissions. Fuel tax increases are an effective way to reduce energy consumption and carbon emissions, but is less effective at reducing other emissions or other mileage-related costs. One of the most appropriate emission reduction strategies is to eliminate current fuel subsidies (Koplow 2010).


Raising fuel price has two effects, it causes modest reductions in vehicle mileage, and over the long term encourages motorists to choose more fuel-efficient vehicles. A 10% price increase typically reduces fuel consumption by about 3% within one year and 7% over a five to ten year period (Elasticities). About one-third of the long-term energy savings result from reduced driving, and about two-thirds results from consumers shifting to more fuel-efficient vehicles.


It is uncertain how much increased fuel efficiency reduces emissions other than CO2. Manufactures design vehicles to meet specific emission standards, and so implement more control strategies in vehicles with larger engines than in vehicles with smaller engines. Some emission control strategies reduce fuel efficiency (for example, catalytic converters add weight, and tuning engines to minimize NOx emissions increases fuel consumption). Reducing vehicle weight and wind resistance tends to reduce non-tailpipe emissions such as tire particles and road dust, but these effects are difficult to quantify. Most emissions decline in proportional to mileage. For example, one study estimates that a fuel tax increase of 50¢ per gallon (US 1991 dollars) would reduce mileage by about 4%, energy consumption by about 9%, and other emissions by about 3.5% (Table 10).


Table 10          Fuel Tax Increase (Harvey and Deakin, 1998, Table B.8)


Tax Increase









- 3.6%






Bay Area
































San Diego
















South Coast








Tax Increase = additional fuel taxes applied in addition to current taxes. VMT = change in total vehicle mileage. Trips = change in total vehicle trips. Delay = change in congestion delay. Fuel = change in fuel consumption. ROG = a criteria air pollutant. Revenue = annual revenue in millions of 1991 U.S. dollars. See original report for additional notes and data.



Since taxes represent about half of total fuel prices in North America, a 20% tax increase is required to produce a 10% price increase. Fuel prices can be increased through Market Reforms such as a revenue-neutral tax shift (increasing fuel taxes and using the revenue to reduce other taxes that are considered more economically harmful, such as taxes on employment and business activity). Such tax shifts can provide Economic Development benefits by reducing employment and investment costs, reducing the economic costs of imported petroleum, stimulating energy efficiency technological innovation, and encouraging consumers to shift their expenditures to goods that generate greater regional employment (Goldstein, 2007). Shapiro, Pham and Malik (2008) used the U.S. Department of Energy’s National Energy Modeling System (NEMS) to evaluate the economic impacts of a carbon tax that begins at $14 per ton of CO2 equivalent and increases to $50 per ton, with 90% of the revenues returned to households and businesses in tax relief and the remaining 10% of revenues used to support energy and climate-related research and development, and new technology deployment. They conclude that this can reduce climate change emissions by 30% while only reducing 2010-to-2030 GDP growth from 33.6% to 33.4%.



Freight Transport Management

Freight and commercial transport represents about 40% of transportation energy consumption, and a somewhat smaller but still significant portion of pollution emissions. Diesel freight vehicles tend to produce high particulate and sulphur emissions, although, as described earlier, these are declining as more rigorous emission control standards are implemented. Some studies estimate that freight energy efficiency can realistically increase by 15-30% over a 10-20 year period (OECD/IEA, 2001, p. 157). The specific strategies described below can increase freight efficiency and reduce pollution.


·         Increase freight vehicle fuel efficiency and reduce emissions through design improvements and new technologies. These include increased aerodynamics, weight reductions, reduced engine friction, improved engine and transmission designs, more efficient tires, and more efficient accessories.


·         Encourage shippers to use more energy efficient modes, such as rail and water transport rather than trucking for longer-distance shipping.


·         Improve rail and marine transportation infrastructure and services to make these modes more competitive with trucking. (Note that by reducing shipping costs this may increase total freight traffic volumes, resulting in little or no reduction in energy consumption, emissions or other externalities.)


·         Improve scheduling and routing to reduce freight vehicle mileage and increase load factors (e.g., avoiding empty backhauls). This can be accomplished through increased computerization and coordination among distributors.


·         Organize regional delivery systems so fewer vehicle trips are needed to distribute goods (e.g., using common carriers that consolidate loads, rather than company fleets).


·         Reduce total freight transport by reducing product volumes and unnecessary packaging, relying on more local products, and siting manufacturing and assembly processes closer to their destination markets.


·         Use smaller vehicles and human powered transport, particularly for distribution in urban areas.


·         Implement fleet management programs that increase system efficiency, use optimal sized vehicles for each trip, and insure that fleet vehicles are maintained and operated in ways that minimize pollution emissions.


·         Encourage retrofit or scrapping of older, higher-polluting freight vehicles.


·         Increase land use Accessibility by Clustering common destinations together, which reduces the amount of travel required for goods distribution.


·         Pricing and tax policies to encourage efficient freight transport.


·         Improve vehicle operator training to encourage more efficient driving.



One estimate of potential truck energy efficiency strategies is listed below (

Aerodynamics                   28%

Driver training                   19%

Strategic measures         14%

Vehicle selection              12%

Improved maintenance                11%

Fuel management           10%



Aviation Transport Management

Aviation is a major source of energy consumption and pollution emissions, is one of the fastest growing transportation sectors, has relatively high fuel consumption rates per passenger-mile (see Table 2), and tends to stimulate increased travel. High altitude air pollution emissions by jets tend to impose particularly high greenhouse impacts, and aircraft cause local air and noise pollution problems. Aviation represents about 10% of current transportation energy consumption.


Although some air travel is relatively inelastic (which is why airlines can sell high-priced business-class seats), much air travel is highly price sensitive (which is why airlines offer discounted fares), so even modest price increases can reduce air travel. Since fuel represents about 10% of total air travel costs, this suggests an elasticity of air travel with respect to total operating costs of about –1.0 or greater. Various policies and management strategies can encourage more efficient, less polluting air travel, and shifts to other modes, particularly to rail and bus for medium-distant trips (200-800 miles). These include:


·         Eliminate airport infrastructure property tax exemptions, and increase aviation fuel tax rates. Eliminate duty-free shops at airports.


·         Increase airport user fees to provide full cost recovery of airport infrastructure investments, air traffic controls and security services.


·         Support development of fast and efficient rail transport on busy corridors to compete with air transport for medium-distance journeys.


·         Upgrade and replace older aircraft with newer models that reduce fuel consumption, noise and air pollution emissions.


·         Improve air traffic management systems to increase operational efficiency.



TDM Programs

Various types of programs implement specific TDM services within a particular geographic areas or group. Many TDM strategies need such a program to be implemented. Such a program has stated goals, objectives, a budget, staff, and a clear relationship with stakeholders. It may be a division within a transportation or transit agency, an independent government agency, or a public/private partnership. Below are examples.


Table 10          TDM Programs

Program Type


Travel Affected

Commute Trip Reduction (CTR) Programs

Employees in a particular business or jurisdiction.

Commute trips (about 25% of personal travel).

Transportation Management Association

Employees, businesses and clients in a district or jurisdiction.

Personal and some freight travel within an area.

Campus Transport Management

Serves students, staff and visitors in a college, university or research campus.

Commutes, and sometimes other trips.

School Transport Management

Serves students, parents and staff within a school.

School trips (about 5% of personal travel).

TDM Programs

Businesses, employees, residents and visitors within a district or jurisdiction.

Travel in the affected area.

Tourist Transport Management

Visitors, businesses and staff.

Travel in resort areas. Any leisure travel.

Special Event Transport Management

Participants and staff at special events, and travelers during emergencies.

Affected travel.



TDM programs typically include some of the following strategies:

·         Commuter Financial Incentives (Parking Cash Out and Transit Allowances).

·         Rideshare Matching.

·         Parking Management and Parking Pricing.

·         Alternative Scheduling (Flextime and Compressed Work Weeks).

·         Telework.

·         TDM Marketing and Promotion.

·         Guaranteed Ride Home.

·         Walking and Cycling Encouragement.

·         Walking and Cycling Improvements.

·         Bicycle Parking and Changing Facilities.

·         Land use planning that reflects Location-Efficient Development principles.

·         Amenities such as on-site childcare, restaurants and shops, to reduce the need to drive for errands.



Pay-As-You-Drive Vehicle Insurance and Other Distance Based Fees

Pay-As-You-Drive (PAYD) pricing means that fixed vehicle fees such as insurance and registration charges are converted into variable fees. For example, a motorist who now pays $1,000 per year for insurance would instead pay about 8¢ per mile, which gives motorists a new opportunity to save money if they driving less. Other fees, such as vehicle registrations, licensing, taxes and lease fees can also be made distance-based.


PAYD pricing can provide a variety of benefits:

·         Increased equity (fees more accurately reflect the costs imposed by each vehicle).

·         Increased affordability (motorists can minimize their insurance and registration fees by minimizing their mileage, which is not currently possible).

·         Reduced uninsured driving (increased affordability can help lower-income and low-annual mileage motorists afford insurance coverage).

·         Reduced crash risk (reduced mileage reduces crashes, and PAYD insurance gives higher-risk motorists the greatest incentive to reduce their mileage).

·         Reduced traffic congestion.

·         Road and parking costs savings.


Converting vehicle insurance and registration fees to PAYD approximately doubles variable vehicle expenses. This is predicted to reduce vehicle travel by approximately 10%, or 12% if vehicle registration fees are also distance-based. Because this involves changes to existing vehicle charges rather it should face less political opposition than a new fee or tax. It can be implemented as consumer option (just as consumers are able to choose a telephone or Internet service rate structure).



Market Reforms

A number of Transportation  and Land Use market reforms can help reduce energy consumption and pollution emissions, and encourage more efficient land use. These include:


·         Full cost pricing (also called marginal cost pricing), which means that users pay directly for costs imposed on society by their vehicle use. This can include direct road user fees, parking pricing, insurance pricing reforms, tax reforms (for example, charging property taxes on road rights-of-way), and vehicle emission fees.


·         Revenue-neutral tax shifts. Since governments must tax something to raise revenue, many economists recommend shifting taxes from socially desirable activities to activities that impose external costs. For example, fuel taxes and other road user charges could increase, and the revenues used to reduce employment and business taxes.


·         More neutral tax policies. Some current tax policies unintentionally favor automobile use. For example, tax policies encourage employers to provide company cars or offer generous mileage reimbursement rates as a perk, and parking is often taxed at a lower rate than other goods.


·         Least-Cost Transportation Planning. Least-Cost Planning means that demand management strategies are given equal consideration as capacity expansion in planning and funding.


·         Cost-based development and utility fees. Clustered development tends to have lower public service costs, but these savings are not generally reflected in development and utility fees. More cost-based pricing can encourage more infill development.


·         Improved transportation pricing methods. Conventional parking pricing and road tolling systems are inconvenient and expensive to operate. New Pricing Methods can overcome these problems, making direct user charges more feasible and politically acceptable.



There is virtually no technical limit to how much these strategies can reduce transportation energy consumption and emissions, their barriers are primarily political and institutional. Transportation market reforms justified on efficiency grounds (such as more efficient pricing of roads, parking and vehicle insurance) could reduce VMT by about one third, plus additional long-term travel reductions from more efficient land use development patterns (Litman 2014).



Land Use Management Strategies

Land use management strategies such as Smart Growth, New Urbanism, Transit Oriented Development, and Location-Efficient Development can reduce per capita automobile use, transportation energy use and emissions by improving Accessibility and Transportation Options (Donoso, Martinez and Zegras 2006). A U.S. Environmental Protection Agency study identified substantial energy conservation and emission reductions if development shifts from the urban fringe to infill (USEPA 2007). The study found that individual households that shift from urban fringe to infill locations typically reduce VMT and emissions by 30-60%, and in typical U.S. cities, shifting 7-22% of residential and employment growth into existing urban areas could reduce total regional VMT, congestion and pollution emissions by 2-7%.


Land use reforms can provide a number of benefits (Land Use Evaluation). Increased land use density and mix tend to reduce total per capita emissions (Boarnet and Handy 2010; Lawrence Frank and Company 2005; TRB 2009), although it can increase exposure to local emissions such as carbon monoxide, particulates and noise. Ewing, et al. (2007), provide detailed analysis of the ability of Smart Growth land use policies to reduce emissions; they estimate the cost effective land use changes can provide energy conservation benefits comparable to shifting average motorists to hybrid vehicles, while providing other economic, social and environmental benefits. In a study comparing per capita carbon emission rates by U.S. metropolitan regions, Sarzynski, Brown and Southworth (2008) found that “density, concentration of development, and rail transit all tend to be higher in metro areas with small per capita footprints. Much of what appears as regional variation may be attributed to these spatial factors.”


The following land use factors can affect energy consumption and emissions (Land Use Impacts on Transportation):


·         Density (the number of people and businesses in a given area) and Clustering (common destinations located close together) affects the distances that people must travel, and the potential of transit, walking and cycling.


·         Land use mix (the diversity of land uses in an area) affects trip distances and the feasibility of nonmotorized transportation.


·         Major activity centers (locate employment, retail and public services close together in walkable commercial centers) increases the feasibility of transit use and allows people to make personal and business errands without driving.


·         Parking management (flexible minimum parking requirements, shared parking, priced parking and regulations to encourage efficient use of parking facilities) affects the relative price and convenience of driving, and affects land use density, accessibility and walkability.


·         Street connectivity (the degree to which streets connect to each other, rather than having deadends or large blocks) affects accessibility, including the amount of travel required to reach destinations and the relative speed and convenience of cycling and walking.


·         Transit Oriented Development (locating high-density development around transit stations) makes transit relatively more convenient, and can be a catalyst for other land-use changes (CNT 2010).


·         Pedestrian Accessibility (walkability) and Traffic Calming (roadway design features that reduce traffic speeds) affect the relative speed, convenience and safety of nonmotorized transportation.



Although individually each of these factors has relatively modest travel impacts, residents of traditional communities that incorporate most or all of these factors tend to drive 20-40% less than otherwise comparable residents of automobile-dependent communities (Land Use Impacts on Transport). Research by Kenworthy (2007) indicates that residents of North American cities consume about 60 MegaJoules annually for transportation energy, about twice that in Canada and Australia, four times that of Western Europe, and six times that of High Income Asian cities, due to differences in transportation and land use policies. A USEPA study (2004) found that regardless of population density, transportation system design features such as greater street connectivity, a more pedestrian-friendly environment, shorter route options, and more extensive transit service tend to reduce per-capita vehicle travel, pollution emissions, congestion delays and traffic accidents.



Nonmotorized Transportation Improvements and Encouragement

Shifts from automobile to nonmotorized transportation can be particularly effective at energy conservation and emission reductions by reducing short motor vehicle trips which have high per-mile fuel consumption and emission rates. As a result, each 1% shift of mileage from automobile to nonmotorized modes tends to reduce energy consumption and pollution emissions by 2-4%. A short pedestrian or cycle trip often replaces a longer automobile trip (for example, consumers may choose between shopping at a local store or driving to a major shopping center). Nonmotorized transportation improvements are also important for increasing transit use and creating more Accessible land use patterns.


Petritsch, et al. (2008) develop a model for predicting the mode shifts and energy savings likely to result from the addition of a particular cycling facility. According to some estimates, 5-10% of urban automobile trips can reasonably be shifted to non-motorized transport (Pedestrian Improvements). Walking and cycling improvements can help reduce total travel: a short walking or cycling trip replaces a much longer automobile trip, and nonmotorized travel improvements support transit use and more accessible development patterns. Some pedestrian-friendly communities have 5-10 times as many nonmotorized trips as occurs in more Automobile Dependent communities with otherwise similar demographic and geographic conditions.


Frank, et al. (2011) used detailed data on various urban form factors to assess their impacts on vehicle travel and carbon emissions. Their analysis indicates that increasing sidewalk coverage from a ratio of 0.57 (the equivalent of sidewalk coverage on both sides of 30% of all streets) to 1.4 (coverage on both sides of 70% of all streets) could reduce vehicle travel 3.4% and carbon emissions 4.9%. Based on the study results the team developed and tested a spreadsheet tool that can be used to evaluate the impacts of urban form, sidewalk coverage, and transit service quality and other policy and planning changes suitable for neighborhood and regional scenario analysis.




Ridesharing refers to carpooling and vanpooling. Carpooling uses participants’ own automobiles. Vanpooling uses vans that are usually owned by an organization (such as a business, non-profit, or government agency) and made available specifically for commuting. Vanpooling is particularly suitable for longer commutes (10 miles or more each way). Ridesharing can be the most cost effective transportation mode. Carpooling that makes use of existing vehicle seats that would otherwise travel empty have very low incremental costs. Vanpooling with 6 or more passengers in a vehicle tends to have the lowest average cost per passenger-mile, since it carries more passengers per vehicle than a carpool, and does not require a professional driver or empty backhauls like conventional public transit services.


There are several ways to support and encourage ridesharing, including providing rideshare matching and vanpool organizing services, Marketing, Commuter Financial Incentives and HOV Priority.



Road Pricing

Road Pricing means that motorists pay directly for using a particular roadway or driving in a particular area. Road Pricing can be implemented as a demand management strategy, to fund roadway improvements or for a combination of these objectives. Economists have long advocated Road Pricing as an efficient and equitable way to pay roadway costs and encourage more efficient transportation. Below are specific types of road pricing


·         Toll Roads are a common way to fund highway and bridge improvements. This is considered more equitable and economically efficient than other roadway improvement funding options.


·         Congestion Pricing (also called Value Pricing) refers to road pricing used to reduce peak-period vehicle travel.


·         High Occupancy Toll (HOT) lanes are High Occupancy Vehicle lanes that also allow access to low occupancy vehicles if drivers pay a toll. This allows more vehicles to use HOV lanes while maintaining an incentive for mode shifting, and raises revenue.


·         Cordon (Area) Tolls are fees paid by motorists for driving in a particular area, usually a city center during weekdays. This can be done by simply requiring vehicles driven within the area to display a pass, or by tolling at each entrance to the area.


·         Vehicle Use Fees such as mileage-based charges can be used to fund roadways and reduce vehicle travel (Distance-Based Fees).



Transit Improvements and Incentives

A variety of strategies can encourage transit use, including increased service, more convenient and comfortable service, transit priority traffic management, lower fares, improved marketing, commuter incentives (such as employee transit benefits), improved pedestrian and bicycle access to transit stops, and Transit Oriented Development. In most communities, 5-10% of automobile trips could shift to transit if these strategies are widely implemented.


Transit consumes less energy and produce less pollution per passenger-mile than automobile travel, and people who rely on transit tend to travel fewer passenger-miles than motorists, so increased transit tends to reduce per capita energy consumption and pollution emissions. A variety of factors affect the energy conservation and emission reduction impacts of transit improvements and incentives (Transit Evaluation). A full transit vehicle consumes less than 10% of the energy per passenger-mile as automobile travel, but in practice system-wide energy savings tend to be smaller due to relatively low load factors (transit vehicles often make trips with relatively few passengers).


Strategies that increase transit load factors (for example, fare discounts, more comfortable vehicles and better information, that increase ridership on routes that have excess capacity) can provide significant emission reductions. Transit improvements can provide a catalyst for broader travel and land use change. For example, people who commute by transit do not usually drive for errands during their breaks, and attractive transit service may allow some households to give up a second car, resulting in reduced per capita automobile travel. Transit Oriented Development helps create multi-modal communities where residents and employees drive less overall (Land Use Impacts on Transport). Some research indicates that each passenger-mile of rail travel represents 3 to 6 miles of reduced automobile travel if a transit system provides a catalyst for more accessible land use, suggesting that total energy saving and emission reduction benefits may be many times greater than what results directly from passenger-miles shifted from automobile to transit (Transit Evaluation).


Wright and Fulton (2005) find that a combination of Bus Rapid Transit and nonmotorized transportation improvements can provide substantial emission reductions at relatively low cost ($14-$66 per tonne of CO2 reduced, compared with $148-3,500 per tonne for introduction of alternative fueled vehicles). Davis and Hale (2007) estimate that at current levels of use public transit services avoid emissions of at least 6.9 million metric tonnes of CO2 equivalent by substituting for automobile travel and reducing traffic congestion, and possibly much more by creating more accessible land use patterns. They estimate that a typical household could reduce its total greenhouse emissions by 25-30% by shifting from two to one vehicles, as can occur if they shift from an automobile-dependent lifestyle to a multi-modal lifestyle. Bailey (2007) found that a typical household reduces its annual mileage 45% by shifting from an automobile-dependent location, which provides minimal travel options and requires ownership of two cars, to a transit-oriented neighborhood, which offers quality transit service and requires ownership of just one car. This saves 512 gallons of fuel annually, worth $1,400 at $2.73 per gallon. ICF International (2008) found that high quality public transit service reduces energy consumption and pollution emissions directly, and also indirectly by creating more accessible and multi-modal land use patterns.



Parking Management and Parking Pricing

Parking Management and Parking Pricing strategies are an effective way to reduce automobile travel, and tend to be particularly effective in urban areas where pollution problems are greatest. Charging motorists directly for the parking tends to reduce automobile trips by 10-30% of affected trips. Parking management and pricing supports use of alternative modes, improves walkability, and encourages more efficient land use.  Also, by reducing the total amount of pavement in an area they help reduce Heat Island Effects (increased ambient temperatures in paved areas) which tends to increase ozone (Gorsevski, et al, 1998).



TDM Marketing

TDM Marketing includes activities that provide consumer information and encouragement to support TDM. Marketing can have a major impact on TDM program effectiveness. Some TDM marketing programs have reduced automobile travel more than 10%.  TDM marketing includes:

·         Educating public officials, businesses about TDM strategies they can implement.

·         Informing potential participants about TDM options they can use.

·         Identifying and overcoming market barriers to the use of alternative modes.

·         Promoting benefits and changing public attitudes about alternative modes.



Traffic Calming and Roundabouts

Traffic Calming includes a variety of roadway design features that reduce vehicle traffic speeds and volumes. The energy and emission impacts depend on project design and conditions. Some Traffic Calming strategies result in smoother traffic and more optimal speeds, reducing energy consumption and emissions. In particular, Modern Roundabouts that replace stop signs and traffic signals can improve traffic flow ( Other Traffic Calming strategies increase stop-and-go driving and reduce traffic speeds below optimal vehicle efficiency (i.e., below 20 mph), and so may increase per-mile vehicle energy consumption and emissions. Impacts on per capita energy consumption and emissions depend on whether Traffic Calming reduces total vehicle travel by making alternative modes and more accessible urban neighborhoods relatively more attractive.



 Car-Free Planning and Vehicle Restrictions

Comprehensive Car-free Planning and Vehicle Restrictions can reduce vehicle use, energy consumption and emissions, if implemented as part of a comprehensive program to increase transportation and land use efficiency. If applied on a small scale, such as a single street or commercial centers, it may simply shift when and where driving occurs, causing little or no energy savings or emission reduction benefit. Some types of vehicle restrictions, such as no-drive days based on license plate numbers, are used during extreme air pollution emergencies, but are probably not effective as long-term strategies. Some households will even purchase a second car to use during their regular vehicle’s no-drive days, or rely on taxis rather than personal automobiles.




Telework involves the use of telecommunications to substitute for physical travel. This includes telecommuting, distance learning, and various forms of electronic business and government activities. According to some estimates up to 50% of all types of jobs are suitable for Telework, but the actual portion of trips that can be reduced by telework appears to be much lower, since many jobs require access to special materials and equipment, or frequent face-to-face meetings, and not all employees want to telework or have suitable home conditions. A portion of the reduced travel is often offset by additional vehicle trips teleworkers make to run errands, and because it allows employees to move further from their worksite, for example, choosing a home of job in a rural area or another city because they know that they only need to commute two or three days a week.



Speed Reductions

Traffic speeds reductions can reduce energy consumption and emissions in two ways. Lower speeds tend to reduce total vehicle mileage. The elasticity of vehicle travel with respect to travel time is  –0.2 to –0.5 in the short run and –0.7 to –1.0 over the long run, meaning that a 10% reduction in average traffic speeds reduces affected vehicle travel by 2-5% during the first few years, and up to 7-10% over a longer time period (Transport Elasticities).


In addition, vehicle fuel consumption and emissions tend to increase at speeds greater than 55 miles per hour, as indicated in figures 1 and 2. For a typical car, fuel efficiency declines about 1% for each additional mile above 55 mph. Reducing travel speeds from 65 to 55 mph provides about 10% fuel savings for a 1997 model vehicle, and about 18% for a 1984 model vehicle. Some researchers suggest that significant energy savings and emission reductions could be achieved by enforcing existing traffic speed limits (Suzuki, 1998).



Sustainable Transportation Planning

Sustainable Transportation refers to transportation systems that respond to long-term and indirect economic, social and environmental objectives. Global air pollution and depletion of non-renewable resources are major concerns for Sustainable Transportation. Sustainable Transportation planning can provide a framework for implementing energy conservation and emission reduction strategies.



Other Strategies

Energy conservation and emission reduction strategies that do not involve TDM are described below.


Promote Efficient and Low Emission Vehicle Purchases

Information and promotion can encourage consumers and fleet managers to purchase more efficient, less polluting vehicles. U.S. federal law requires vehicle manufacturers to post fuel efficiency ratings on new vehicles, and information resources such as those listed below can help consumers take energy and emission factors into account when selecting a vehicle.


Vehicle Energy Consumption and Emission Information Resources

ACEEE, Green Book; The Environmental Guide to Cars and Trucks, American Council for an Energy Efficient Economy ( and (, 2001. This publication ranks motor vehicles according to their environmental impacts.


AirHead Website ( is an online tool to provide information about the air pollution impacts of their everyday decisions. It can calculate an individual’s air emission profile and track it from month to month.


Fuel Economy Website (, by the U.S. Department of Energy and the U.S. Environmental Agency provides information on fuel consumption ratings of new automobiles and additional information on vehicle efficiency strategies.


NRC, EnerGuide for Vehicles, Natural Resources Canada ( provides information on automobile fuel efficiency in the Canadian market.



Emission Standards

These are requirements that manufacturers produce vehicles that incorporate certain technologies (such as emission catalysts) or meet a maximum emission standard. These have been widely applied and have been successful at reducing per-mile emission rates for some pollutants. Such standards can be increased to force manufactures to develop and implement additional emission controls. McGranahan and Murray (2003) discuss vehicle emission standards suitable for developing countries.


Table 12          U.S. Emission Standards (Grams/Mile) (BTS, 2000, Table 4-6)


Total HC



Cold CO



Passenger Cars







Full Useful Life







Light Trucks







Full Useful Life







This table shows U.S. vehicle emission standards.



Fuel Efficiency Standards

Corporate Average Fuel Efficiency (CAFE) standards require vehicle manufactures to produce and sell more fuel-efficient vehicles. Manufactures pay a fine if the vehicles they sell on average exceed these standards. The current US standard is 27.5 mpg (8.2 liters per 100 kilometers) for passenger cars and 20.2 mpg (11.4 liters per 100 kilometers) for light trucks (BTS, 2000, Table 4.5). These have not increased since 1996. Recent studies have investigated raising these standards in the near future (NRC, 2001; Suzuki, 1998).



Gas Guzzler Taxes

A Gas Guzzler Tax is a special tax on the purchase of new vehicles based on their fuel consumption rates, to encourage the manufacture and sale of more fuel-efficient vehicles. The U.S. Gas Guzzler Tax was established in 1978 and phased in over ten years. Environmental and energy conservation organizations are lobbying to extend this tax to light trucks and SUVs (FOE, 2000).


Table 13          Gas Guzzler Tax Rates (ORNL, 2000, Table 7.19)

Miles Per Gallon



22.5 & Higher

































12.5 & below






Feebates are a surcharge on the purchase of new fuel inefficient vehicles, with the revenue used to provide a rebate on the purchase of fuel-efficient vehicles (Perrin, 2000). The table below indicates the predicted impact of Feebates, based on a 9-liters/100 kilometer base. For example, if a $500 level is used, a vehicle rated at 6 liters/100 km would receive a $1,500 rebate, while a vehicle rated at 11 liters/100 km would be charged a $1,000 fee. Kunert and Kuhfeld (2007) recommend a set of tax reforms to encourage the purchase of more fuel efficient vehicles.


Table 14          Feebate Impacts (1996 U.S. Dollars, based on Michaelis, 1996)

Feebate Level Per Liter/100 kms

New Vehicle Fuel Economy Increase









The table shows the predicted impact of various Feebate levels, based on a 9-liters/100 kilometer base. Purchasers of vehicles that are less efficient pay a fee, and purchasers of vehicles that are more efficient receive a rebate based on the selected rate.



Close Gas Guzzler Loopholes

Current U.S. federal policy is the opposite of a gas guzzler tax. Businesses are allowed to claim an immediate deduction off the price of a light truck or SUV  that weighs over 6,000 pounds, worth as much as $25,000, plus a bonus deduction of 30% of the remaining vehicle cost until 2004. This deduction is not available on lighter vehicles. A large Chevy Suburban qualifies, but the lighter and more fuel efficient Chevy Blazer does not, nor does a standard or fuel efficient car. This provides a significant price cut. Ford Motor Co.'s Land Rover Range Rover, for instance, has a list price of $71,865, but the combined tax breaks effectively knock $21,560 off the price, over the course of five years, assuming a tax rate of 30%. Although originally intended to benefit small farmers, the law is now primarily used by non-farm businesses. (Jeffrey Ball and Karen Lundegaard, “SUVs Get Big Tax Break - As Drivers Seize Loophole,” The Wall Street Journal, December 19, 2002.



Efficiency-Based Annual Registration Fees

An alternative to Gas Guzzler taxes or Feebates on the purchase of a new vehicle is an annual vehicle fee based on a vehicle’s fuel efficiency rating. This can be implemented by modifying the structure of existing vehicle registration fees rather than imposing a new fee. These may induce some motorists to purchase less polluting vehicles. Such fees tend to be regressive, since lower-income motorists are more likely to own a higher-polluting vehicle (Sevigny, 1998).



Transit Emission Reduction Programs

Transit vehicle emission reduction programs can be particularly cost effective because transit vehicles tend to drive high mileage under urban-peak conditions, and older diesel buses had high per-mile emission rates. Such programs include use of electric trolleys and alternative fuel buses (such as natural gas) to replace conventional diesel buses, retrofitting existing buses with cleaner diesel engines, and improving bus maintenance and operating practices (see USEPA “Urban Bus Retrofit/Rebuild” program at



Motorcycle Encouragement

Motorcycles average about 50 miles per gallon (BTS, 2000), about twice the fuel efficiency of an average automobile, so shifts from driving to motorcycling can conserve fuel. Programs can encourage motorcycling and motorcycle safety (VicRoads, 2001). However, motorcycles tend to produce high rates of conventional pollutants because their engines generally lack emission control features such as fuel injection and catalytic systems, and many older motorcycles had high-polluting two-cycle engines. Motorcycles also have low load factors: they tend to be more energy-efficient than a solo driver in an average automobile, but less energy efficient than two or more passengers in a fuel-efficient car.



Super-Efficient and Alternative Fuel Vehicle Incentives

Public agencies can sponsor research, demonstration and marketing programs to develop super-efficient and alternative fuel vehicles and encourage their use (Hypercar; CalStart). The emission reduction benefits from alternative fuels depends on many factors, including the type of fuel and engine used, how the fuel is produced, and whether full lifecycle emissions are considered (Delucchi 2003; Bourne 2007). Implementation strategies include minimizing taxes (or providing tax credits) on high efficiency and alternative fueled vehicles, minimizing taxes on alternative fuels, development and production subsidies and tax credits, government fleet purchases of high efficiency and alternative fueled vehicles, infrastructure support (such as government supply of refueling and recharging stations), mandates and promotion campaigns.



Low and Zero Emission Vehicle Mandates

A Zero Emission Vehicle (ZEV) Mandate was created by California's Air Resources Board (CARB; in accordance with Low-Emission Vehicle (LEV) Regulations passed in 1990. It requires that a portion of vehicles sold in California by major car companies be zero-emission (i.e., virtually no tailpipe emissions). Originally the mandate was to be 2% of vehicles in 1998, increasing to 10% in 2003, but in 1996, CARB changed the requirement to a “good faith effort” by manufactures to market ZEVs.



Inspection and Maintenance (I/M) Programs

This means that vehicles are inspected annually or biannually by a certified emission inspection station to identify those with excessive emission rates ( A typical I/M program fails about 10% of vehicles, which are required to be repaired or scrapped. Repairs resulting from I/M programs are estimated to reduce fleetwide vehicle fuel consumption by about 0.5%, emissions of NOx by 1%, hydrocarbons by 10% and carbon monoxide by 15%. As a larger portion of the vehicle fleet has modern engines with more durable emission controls, the effectiveness of such programs is expected to decline.



Roadside “High Emitter” Identification

Instruments are now available that identify the emission rates of vehicles as they drive pass a sensor (FEAT Data Center,; MDNR 2005). These can be used with voluntary systems (see box below) or legal enforcement to have high emitting vehicles corrected. Some programs encourage police and citizens to report vehicles that appear to emit excessive smoke (


Voluntary Emissions Reduction (

Using input from the public, a new type of vehicle emissions information system has been developed which integrates an innovative variable message sign with an on-road vehicle emissions sensing system to display individual vehicle emissions information to passing drivers. The Smart Sign was successfully operated from May 1995 to August of 1996 in Denver Colorado as part of a Federal Highway Administration Intelligent Transportation System operational test. During that time more than 4 million readings were provided to more than 250,000 individuals at a cost of $0.02/test.


The original deployment was permanently located in Denver at the intersection of Speer Blvd. and Interstate 25. The system operated 7 days a week 24 hours a day in conditions that ranged in temperature from -20 to 100 degrees F. The more than 4 million readings were distributed as 86% “Good”, 10% “Fair” and 4% “Poor”.


Using vehicle information the National Center for Vehicle Emissions Control and Safety conducted a follow-up phone survey which showed that 76% of the weighted population had a favorable impression of the sign. Sixteen percent of vehicles rated “poor” (1.6% of the overall fleet) reported to have already taken corrective action as a result of the Smart Sign.


The Smart Sign system has now been converted to a portable system enabling it to be used in a number of new and innovative applications. The sign has been mounted onto a trailer. The remote sensor is mounted above ground in weather protective housings upstream of the sign.



Scrapage Programs

These programs involve the purchase and disposal of older, higher-emitting vehicles (Dill 2004). This can reduce local pollution emissions, since older vehicles tend to have high emission rates, but does little to reduce energy consumption since older vehicles are on average no more fuel-efficient than new vehicles. Such programs can be set based on vehicle age (i.e., vehicles must be 15 years or older), or vehicles that fail an emission test could qualify. There are potential problems with such programs, since many of the vehicles may be scrapped soon anyway, and some residents may even purchase an older vehicle from another region so it can be purchased through the program. Li, Linn and Spiller (2011) conclude that such programs provide little and costly emission reductions.



Fuel Quality Improvements

Vehicle fuel quality (such as sulphur and heavy metal content) affects the amount of pollution produced per vehicle-mile (SOx, heavy metals, NOx, and particulates), and some fuel contaminants can degrade vehicle emission control equipment. Fuel quality improvements can reduce some pollutants, and may slightly increase vehicle efficiency (Perrin, 2000; Working Group 1 on Environmental Objectives, 2000). Many jurisdictions, including the United States, Canada and some individual states regulate fuel quality. California has been a leader is setting high fuel quality standards. Fuel quality can also be improved by imposing higher taxes on lower-quality fuels or fuels that have harmful additives. This approach has been successful in reducing the use of leaded fuel.



Emission Capping and Trading

Emission Capping places a limit on the total amount of pollution that may be produced in an area. Emission Trading is a market structure that involves allocating or selling pollution rights, and allowing those rights to be traded to allow the most cost-effective emission reduction strategies to be implemented (Albrecht 2000; Neiderberger 2005). For example, if ten factories each receive a 100-ton-per-year emission allocation, those that can reduce emissions at a lower cost can sell their rights to others that have a higher cost per unit of emission reductions.


Emission trading has been effective and efficient at reducing some emissions when there are a small number of emitters (e.g., a few factories), but most analysts conclude that emission trading as it is currently practiced is not practical for reducing transportation emissions, at least at an individual level. Emission trading may allow funding of specific transportation emission reduction programs. For example, discounts



Fleet Management and Driver Training

There are many ways to increase motor vehicle performance and efficiency through best management practices, including regular inspections and maintenance, and improved driver training (Sivak and Schoettle 2011). This is especially appropriate for large vehicle fleets, such as delivery trucks, taxis and vehicle pools (PHH 2001). The FleetSmart Program funded by Natural Resources Canada ( provides information on industrial fleet management for efficiency and safety. The Energy Environment Excellence Fleet Management website ( provides practical information for optimizing vehicle fleet fuel efficiency and environmental performance.


Driver education and training programs can emphasize techniques that reduce fuel consumption. The Eco-Drive Program sponsored by the Swiss Federal Office of Energy promotes energy conservation driving techniques which can increase energy efficiency by 10-15% (SFOE, 2000). It recommends the following driving habits:

·         Drive in the highest possible gear and at the lowest possible number of revolutions.

·         Accelerate briskly.

·         Switch to a higher gear quickly (at a maximum of 2500 revolutions), wait before changing down.

·         Drive steadily and defensively, avoid unnecessary braking and gear changes.


The Repair Our Air-Fleet Challenge ( works with fleets to reduce inefficient fuel consumption through:

·         Idling reduction (commercial vehicles often idle a significant portion of their operating time)

·         Speed management

·         Cab heater alternatives

·         Maintenance practices

·         Driver efficiency




Idling vehicles produce air and noise pollution. FleetSmart (2001) encourages truck drivers to minimize idling. Some communities have passed anti-idling laws that limit how long a vehicle can sit with the engine operating when it is not being driven (CCS, 2001). Some organizations provide information and resources to help reduce unnecessary engine idling ( and  (



Neighborhood Vehicles

These are small, low-speed vehicles, often powered by alternative fuels, suitable for local travel (Sperling 1995). For information see Smart Cars ( and the National Station Car Association ( This type of vehicle can be encouraged by removing any barriers to their legal registration and use of public roads, favorable local transportation policies, roadway designs that accommodate such vehicles, and by direct support from transit agencies.



Resurface Highways

Reducing highway surface roughness through improved maintenance and using less flexible pavement surfaces such as concrete rather than asphalt can reduce fuel consumption by as much as 10% for heavy trucks, and by a smaller amount for lighter vehicles (TC 1999). However, most studies indicate that this is not a very cost effective way to increase fuel efficiency.



Summary of Emission Reduction Strategies

The table below lists the energy conservation and emission reduction strategies described in this chapter (for strategies that appear to be suitable for quick implementation see Noland, Cowart and Fulton, 2005).


Table 15          Summary of Emission Reduction Strategies

Reduces Vehicle Travel (TDM)

Reduces Vehicle Emission Rates

Aviation transport management

Car-free planning and vehicle restrictions

Commute trip reduction programs

Distance based fees

Distance-based emission fees

Freight transport management

Fuel tax increases

Land use management strategies

Market reforms

Nonmotorized transportation

Parking management and parking pricing

Pay-as-You-Drive vehicle insurance


Road pricing

Speed reductions

TDM marketing


Traffic calming and roundabouts

Transit improvements and incentives


Efficiency-based annual registration fees

Emission capping and trading

Emission standards


Fleet management and driver training

Fuel efficiency standards

Fuel quality improvements

Inspection and maintenance (I/M) programs

Low and zero emission vehicle mandates

Motorcycle encouragement

Neighborhood vehicles

Promote purchase of cleaner vehicles

Resurface highways

Roadside “high emitter” identification

Scrapage programs

Super-efficient and alternative fuel incentives

Transit emission reduction programs

This table lists the various types of energy conservation and emission reduction strategies identified in this chapter.



Policy Reforms and Incentives

Governments can implement various reforms and provide incentives for implementation of emission reduction strategies. For example, governments can implement Institutional Reforms such as Least Cost Transportation Planning and Smart Growth Fiscal Reforms within its own jurisdiction.


Governments can perform sustainability audits of its policies, investments and programs to identify how they affect Sustainability objectives, including energy and emission reductions. This process can help prioritize funding allocations and design policies and programs to help achieve sustainability.


Federal, state and provincial governments often provide funding to regional and local governments. Special funding programs can be available for projects that reduce transportation emissions (such as transit and nonmotorized transportation improvements), and all types of grants can be prioritized based on how well they support sustainability objectives. For example, infrastructure funding that encourage efficient transportation and Smart Growth can be given priority over projects which are otherwise equally beneficial, but do not support these objectives. Federal, state and provincial grants can give priority to communities that have efficient transportation and land use policies. Such incentives can motivate communities to implement their own Institutional Reforms and Smart Growth Fiscal Reforms. This can increase the cost effectiveness of infrastructure investments, since efficient transportation and land use policies can reduce unit costs of providing public services such as roads, water, sewage and schools, particularly over the long run.



Congestion-Reduction Strategies

Programs to reduce vehicle traffic congestion are often promoted as ways to save energy and reduce vehicle emissions. For example, Barth and Boriboonsomsin (2009) estimate that reducing severe congestion on Los Angeles freeways (speeds below 30 mph) could reduce freeway travel CO2 emissions by 7-12%.


However, actual benefits are difficult to predict, and often small or negative over the long term if congestion reductions efforts stimulate additional vehicle travel. Traffic speed has different effects on different types of pollutants. Per-mile emissions of most pollutants are high at very low speeds and under stop-and-go conditions, and decline as traffic speeds increase and become steady. NOx emissions are lowest at 20-30 mph and increases at speeds over 45 mph. CO and VOC emissions increase significantly at speeds over 55 mph, as indicated in Figure 2. As a result, strategies that relieve congestion and increase traffic speeds from 25 mph up to 50 mph my reduce CO and VOC emission, but increase NOx emission.


Whether a particular congestion reduction program causes overall reductions or increases in energy use and emissions depends on the specific circumstances, including location, time, change in level of congestion, driving style, and which emissions are considered most harmful. Although extreme traffic congestion that results in stop-and-go driving (Level of Service F) significantly increases energy consumption and emissions, a good portion of urban-peak travel occurs under moderate congestions in which energy consumption and emissions are minimized (Level of Service C or D).


EPA’s latest research indicates that for newer, cleaner vehicles emissions increase at much lower speeds than previously thought. NOx emissions increase with highway speeds above 15-20 miles per hour, VOC emissions increase with speeds above 30-35 mph, and CO above 30. On arterials and local streets emissions increase above 30-35. A congestion reduction program that improves roadway Level of Service from F probably reduces energy consumption and emissions, but shifting Level of Service from D to A probably increases energy consumption and most emissions. Table 16 compares energy consumption and emissions for a typical diesel transit bus under various conditions, showing the effects of higher speeds and traffic congestion.


Table 16          Diesel Transit Bus Energy and Emissions



50 km/h


80 km/hr

Congested Flow

Minor Roads

Arterial Road

CO2 (g/km)






NOx (g/km)






PM10 (g/km)






Fuel (l/100km)






The table shows the emission and energy consumption rates of a typical diesel bus under various driving conditions. Congestion increases emissions and energy consumption.



Congestion reductions tend to induce additional vehicle travel by reducing travel time and vehicle operating costs (Rebound Effects). A less congested roadway allows people to take additional automobile trips that they would forego under more congested conditions. For example, if roads are uncongested you might take a cross-town shopping trip, but choose a closer, more convenient store if roads are congested. Increased roadway capacity may induce some people to choose more distant homes or worksites, resulting in long-term increases in vehicle mileage. This additional travel can increase overall energy consumption and emissions, even if it occurs under less congested conditions.


Recent modeling indicates that roadway capacity expansion reduces energy consumption and emissions in the short term, but in most cases this is soon offset by induced travel (OECD/IEA 2001; Noland and Quddus 2006). Cities with increased roadway capacity tend to have higher per capita transportation energy consumption and emission rates, indicating that congestion reduction efforts are unlikely to reduce overall vehicle energy use or emissions.


Below are congestion reduction strategies that are sometimes promoted as ways to save energy and reduce emissions. Such claims are probably exaggerated or wrong altogether. Current knowledge indicates that efforts to reduce urban traffic congestion by themselves are unlikely to reduce overall vehicle energy consumption or pollution emissions, and are as equally likely to increase it over the long run. Of course, congestion reduction and increased vehicle travel may provide user benefits, but there is little valid evidence that they are justified on environmental grounds.




Flextime means that employees are allowed some flexibility in their daily work schedules. For example, rather than all employees working 8:00 to 4:30, some might work 7:30 to 4:00, and others 9:00 to 5:30. This shifts travel from peak to off-peak periods. By itself it provides no reduction in vehicle mileage, although it can help transit and rideshare commuters match schedules.



Road Capacity Expansion and Traffic Signal Synchronization

Road widening and traffic signal synchronization are sometime advocated as ways to reduce traffic congestion, and therefore energy consumption and pollution emissions (TRB 1995; Cobian, et al. 2009). However, research suggests that at best these provide short-term reductions in energy use and emissions which are offset over the long-run due to Induced Travel (Noland and Quddus 2006). Field test indicate that shifting from congested to uncongested traffic conditions significantly reduces pollution emissions, but traffic signal synchronization on congested roads provides little measurable benefit, and can increase emissions in some situations (Frey and Rouphail 2001). According to a study by the Norwegian Centre for Transport Research (TØI 2009):


“Road construction, largely speaking, increases greenhouse gas emissions, mainly because an improved quality of the road network will increase the speed level, not the least in the interval where the marginal effect of speed on emissions is large (above 80km/hr). Emissions also rise due to increased volumes of traffic (each person traveling further and more often) and because the modal split changes in favor of the private car, at the expense of public transport and bicycling.”



Table 17 summarizes roadway improvement emission impacts, including effects on emission rates per vehicle mile, increases in total vehicle mileage, and emissions from road construction and maintenance activities.


Table 17          Roadway Expansion Greenhouse Gas Emission Impacts (TØI 2009)


General Estimates

Large Cities

Small Cities

Intercity Travel

Emission reductions per vehicle-kilometer due to improved and expanded roads.


Short term reductions. Stable or some increase over the long-term.

Depends on situation, ranging from no change to large emission increases.

Depends on situation. Both emission reductions and increases can occur.

Increased vehicle mileage (induced vehicle travel), short term (less than five years)

A 10% reduction in travel time increases traffic 3-5%

Significant emission growth

Moderate emission growth

Moderate emission growth

Increased vehicle mileage (induced vehicle travel), long term (more than five years)

A 10% reduction in travel time increases traffic 5-10%

Significant emission growth

Moderate emission growth

Moderate emission growth

Road construction and improvement activity

12 tonnes of CO2 equivalent for 2-lane roads and 21 tonnes for 4-lane roads.

Road construction emissions are relatively modest compared with traffic emissions.

Roadway operation and maintenance activity

33 tonnes of CO2 equivalent for 2-lane roads and 52 tonnes for 4-lane roads.

Road operation and maintenance emissions are relatively modest compared with traffic emissions.

This table summarizes roadway improvement emission impacts according to research by the Norwegian Centre for Transport Research.



Intelligent Transportation Systems

Intelligent Transportation Systems include the application of a wide range of new technologies, including driver information, vehicle control and tracking systems, transit improvements and electronic charging (see ITS Online and ITS America). These can provide a variety of transportation improvements, including driver convenience, reduced congestion, increased safety, more competitive transit, and support for pricing incentives. ITE strategies that support transportation demand management reduce total vehicle travel (such as transit improvements and electronic road pricing) can reduce energy consumption and emissions, but not strategies that make driving more convenient, or squeeze more vehicles onto existing roadways, because they are likely to increase vehicle traffic mileage and speeds.



Evaluating Energy Conservation and Emission Reduction Strategies

Several studies have attempted to compare and rank energy conservation and emission reduction strategies in terms of potential effectiveness and cost effectiveness, in order to identify the “best” option (TC 1999; Wright and Fulton 2005). Their conclusions vary significantly based on the assumptions that are used.


Many evaluations ignore Rebound Effects, particularly the tendency of motorists to increase their mileage when increased fuel efficiency reduces per-mile vehicle operating costs. A 10% increase in vehicle fuel efficiency typically results in a 20-30% increase in vehicle mileage, resulting in a 7-8% net energy savings. Ignoring this impact tends to overstate the emission reduction benefit of technical strategies that increase fuel efficiency.


Most evaluations focus on direct implementation costs and emission reduction benefits, ignoring most other costs and benefits. Such an approach may favor strategies that are cost-effective at reducing emissions, but increase other problems such as consumer costs, crash damages or traffic congestion. A more Comprehensive Evaluation Framework considers a broader range of impacts, and so will favor that emission reduction strategies that provide additional benefits, such as consumer cost savings, road safety and congestion reductions (Litman 2005).


Table 18 discusses whether each strategy described in this chapter is likely to cause induced travel, and what additional benefits and costs it is likely to cause. Strategies that reduce perceived vehicle operating costs tend to induce additional vehicle travel, and so tend to increase traffic congestion, facility costs, crashes and urban sprawl. Strategies that increase perceived vehicle operating costs tend to reduce total vehicle travel, and so can provide benefits such as reduced congestion, facility costs, crashes, and urban sprawl. Some strategies also improve consumer choice and savings. The vehicle travel impacts of some strategies depend on how they are implemented.


Table 18          Summary of Rebound Effects and Additional Benefits


Induced Vehicle Travel

Additional Impacts

Distance-Based Emission Fees

None. Increases per-mile vehicle costs.

Can help reduce congestion, road and parking facility costs, crashes and urban sprawl.

Fuel Tax Increases

None. Increases per-mile vehicle costs.

Can help reduce congestion, road and parking facility costs, crashes and urban sprawl.

Freight Transport Management

Depends on which strategies are used.

Depends on which strategies are used. Strategies that reduce vehicle traffic can reduce congestion, roadway costs and crashes.

Aviation Transport Management

Depends on which strategies are used.

Depends on which strategies are used. Strategies that reduce air travel can reduce airport congestion, consumer costs and crashes.

TDM Programs

Depends on which strategies are used.

Strategies that reduce vehicle traffic can reduce congestion, roadway costs and crashes.

Pay-As-You-Drive Vehicle Insurance

None. Increases per-mile vehicle costs.

Can help reduce congestion, road and parking facility costs, crashes and increased equity.

Land Use Management Strategies


Depends. Can reduce crashes, increase transportation choices, reduce sprawl and increase community livability.

Nonmotorized Transportation Improvements


Can reduce congestion, road and parking facility costs, sprawl, and increase transport choices and community livability.

Consumer Information

If it encourages motorists to purchase more fuel-efficient vehicles than they would otherwise it may cause some induced travel.

Depends. Improves consumer choice and financial savings.

Road Pricing

Generally none, unless it significantly increases total roadway capacity and automobile dependency.

Depends on the type of pricing and how revenues are used. Can reduce congestion, road and parking facility costs, crashes and sprawl.

Transit Improvements and Transit Vehicle Emission Reductions


Can reduce congestion, road and parking facility costs, sprawl, and increase transport choices and community livability.

Rideshare Programs

May encourage longer commutes.

Can reduce congestion, road and parking facility costs, sprawl, and increase transport choices.

Parking Management


Can reduce congestion, road and parking facility costs and sprawl.

Traffic Calming and Roundabouts


Can reduce crash risk and increase community livability.

Vehicle Restrictions

None, unless it only applies to a small area and causes travel to shift elsewhere.

Can reduce congestion, road and parking facility costs, sprawl, and increase transport choices and community livability.


Possible. Telecommuters may take additional non-commute trips or move farther away from their worksite.

Reduces traffic congestion, crashes, road and parking facility costs and improves commuter choice and savings. May contribute to sprawl.

Emission Control Standards

Generally none, unless it also reduces vehicle operating costs.


Fuel Efficiency Standards

Yes. Reduces vehicle operating costs and so tends to increase vehicle mileage.

Tends to increase traffic congestion, road and parking facility costs, crashes and sprawl.

Gas Guzzler Taxes

Yes. Reduces vehicle operating costs and so tends to increase vehicle mileage.

Tends to increase traffic congestion, road and parking facility costs, crashes and sprawl.


Yes. Reduces vehicle operating costs and so tends to increase vehicle mileage.

Tends to increase traffic congestion, road and parking facility costs, crashes and sprawl.

Efficiency-Based Annual Registration Fees

Yes. Reduces vehicle operating costs and so tends to increase vehicle mileage.

Tends to increase traffic congestion, road and parking facility costs, crashes and sprawl.

Super-Efficient and Alternative Fuel Incentives

Yes. Reduces vehicle operating costs and so tends to increase vehicle mileage.

Tends to increase traffic congestion, road and parking facility costs, crashes and sprawl.

Motorcycle Encouragement

Probably. Reduces vehicle operating costs and so increase vehicle mileage.

Tends to increase crash injuries and deaths.  Often increases conventional air pollutants (since few motorcycles have emission control equipment). Reduces parking costs.

Low and Zero Emission Vehicle Mandates

Probably. Reduces vehicle operating costs and so increase vehicle mileage.

Tends to increase traffic congestion, road and parking facility costs, crashes and sprawl.

Inspection and Maintenance (I/M) Programs

Probably. May reduce vehicle operating costs by a small amount.

Uncertain. May increase traffic congestion, road and parking facility costs, crashes and sprawl, but impacts are likely to be small.

Roadside "Hig Emitter" Identification

Unlikely. May reduce vehicle operating costs by a small amount.


Scrapage Programs

Probably none.

May increase road safety by reducing the number of old vehicles on the roadway.

Fuel Quality Improvements

Uncertain. May increase fuel costs but increase fuel efficiency.

Uncertain. Probably minimal.

Emission Capping and Trading

Depends on how the program is implemented.

May involve TDM strategies.

Fleet Management

Uncertain. May reduce vehicle-operating costs and reduce vehicle mileage.

Depends on what measures are implemented.

Speed Limit Enforcement

None. Tends to increase per-mile time costs and so reduce total mileage.

Can reduce crashes and sprawl, and increase community livability.


Probably none.

Can increase community livability due to reduced local air and noise pollution.

Neighborhood Vehicles

None. Likely to reduce total vehicle mileage.

Mixed impacts. Likely to increase consumer choice and community livability.

Resurfacing Highways

Probably. Reduces vehicle operating costs and increases comfort.

May increase traffic congestion, road and parking facility costs, crashes and sprawl.


Probably. Reduces traffic congestion, which is likely to induce vehicle travel.

Reduces peak-period traffic congestion.

Road Capacity Expansion/Traffic Signal Synchronization

Yes. Reduces traffic congestion and vehicle operating costs, inducing additional vehicle travel.

Likely to increase downstream traffic congestion, road and parking facility costs, crashes, sprawl and automobile dependency, particularly over the long-run.

Intelligent Transportation Systems

Depends on which are implemented.

Strategies that reduce congestion and increase vehicle speeds and volumes may increase some costs.

This table indicates whether a strategy is likely to induce additional vehicle travel by reducing per-mile vehicle operating costs, and other benefits and costs that it is likely to cause.



Emission Reduction Equity Analysis (

Lin (2008) evaluates climate change policies in terms of their equity impacts, including the distribution of damages from climate change and other air pollutants (impacts such as power plant emissions and reduced fish and game are particularly concentrated on low income and minority communities), and the distribution of benefits from emission reduction efforts (such as whether energy conservation programs provide incentives and jobs to low income and minority populations). She critiques emission reduction policies, such as cap-and-trade, feebates and road pricing in terms of their impacts on disadvantaged populations, and recommends specific design principles (such as insuring adequate alternative travel modes if congestion pricing or carbon taxes are implemented, and use of revenues in ways that benefits disadvantaged populations.


Efficient Vehicles Versus Efficient Transportation

Many transportation professionals have a personal preference for technological strategies that increase vehicle fuel efficiency and reduce per-mile emissions over TDM strategies that reduce automobile mileage, on the assumption that this maximizes social benefits, since vehicle mileage reductions require consumers to forego travel or shift to slower modes. However, this assumption if often wrong. Mileage reduction strategies based on positive incentives (for example, by improving alternative modes or giving consumers a financial reward for reduced driving) benefit consumers directly, as well as providing additional social benefits such as congestion reductions, reduced crashes, road and parking facility costs savings, and more efficient land use (Evaluation). When all factors are considered, mileage reductions are often the most cost-effective way to reduce energy consumption and emissions, and make consumers better off overall (Win-Win Transportation Solutions).


Of course, there is seldom a need to choose between vehicle efficiency improvements and TDM. Demand management strategies can be implemented in conjunction with vehicle design improvements, so that consumers have opportunities and incentives to avoid unnecessary vehicle travel, and any driving they do is in an efficient, low-polluting vehicle.


Wit and Humor

Economists often emphasize the importance of “internalizing” costs, meaning that users bear the costs direct, rather than imposing them on other people.

It’s easy to internalize motor vehicle air pollution costs. Simply connect the exhaust pipe directly into the passenger compartment. Of course, that’s also called suicide.



Best Practices


·         Consider a wide range of energy conservation and emission reduction strategies.


·         Consider a variety of impacts besides energy conservation and emission reductions, including impacts on consumer costs and transportation choice, congestion, parking costs, road safety, equity and community livability.


·         Account for the rebound effects of strategies that reduce per-mile vehicle operating costs.


·         Consider additional costs and benefits, including social costs (congestion, crashes, facility costs, sprawl, etc.) that result from any induced vehicle travel, and benefits that result from reductions in vehicle travel.


·         Consumer surplus analysis can be used to evaluate the impacts that TDM strategies have on consumers. Strategies that use positive incentives (improved transportation choices and financial benefits) tend to make consumers better off overall, while strategies that use negative incentives (such as road and parking pricing) tend to cause direct reductions in consumer surplus (minus any social benefits and revenues).


·         In most cases a package of complementary strategies is the most effective and cost-effective way to reduce energy consumptions and emissions.


·         In most cases, congestion reductions by themselves will not reduce vehicle energy consumption or emissions over the long run.



Examples and Case Studies

Local Emission Reduction Modelling

Jones, Wheeler and Kammen (2018) quantify the potential of local policies and programs to meet aggressive GHG reduction targets using a consumption-based, high geospatial resolution planning model for the state of California. We find that roughly 35% of all carbon footprint abatement potential statewide is from activities at least partially within the control of local governments. The study shows large variation in the size and composition of carbon footprints and abatement opportunities by 23,000 Census block groups (i.e., neighborhood-scale within cities), 717 cities and 58 counties across the state. These data and companion online tools can help cities better understand priorities to reduce GHGs from a comprehensive, consumption-based perspective, with potential application to the full United States and internationally.


Vision California Identifies Smart Growth Emission Reductions (

Vision California is a strategic planning program that explores the role of land use and transportation investments in meeting the environmental, fiscal, and public health objectives. Vision California uses the new Rapid Fire Model, a user-friendly spreadsheet tool that evaluates regional and statewide land use and transportation scenarios, including various combinations of land use density, mix, building types and transport policies, and predicts their impacts on vehicle travel, pollution emissions, water use, building energy use, transportation fuel use, land consumption, and public infrastructure costs. All assumptions are clearly identified and can be easily modified.




More than 17,000 people have so far called the 0800 SMOKEY hotline since the Auckland Regional Council's campaign, targeting vehicles with smoky exhausts, was launched on August 14.  All motorists identified receive a letter from the ARC offering the vehicle owner a free exhaust emission test and a suggestion to tune their vehicles regularly.


The initiative has been set up to address the problem that air quality in some inner-city Auckland streets regularly exceeds World Health Organisation standards.  Carbon monoxide levels in Auckland are higher than in London. Over 80% of Auckland’s air pollution comes from motor vehicle emissions, compared with 3% from industry.  Tuning vehicles regularly will also improve vehicle fuel economy. More information is at: and



50 Transportation Emission Reduction Strategies (Dutzik 2016)

The report, ), 50 Steps Toward Carbon-Free Transportation:  Rethinking U.S. Transportation Policy to Fight Global Warming, identifies fifty ways that public policies can encourage more energy efficient and lower-polluting transportation. It describes a New Transportation Toolbox of strategies that – especially if combined in ways that maximize synergies among them – can help to create a zero-carbon transportation system. Among those strategies are:

Repowering Vehicles: Efficient electric vehicles that can be powered by clean, renewable electricity are entering the marketplace faster than the hybrid cars of a decade ago, and technology continues to improve, reducing costs and increasing travel range. Electric vehicles reduce carbon emissions even when using electricity from today’s grid, and will deliver greater benefits in the years to come as America transitions to electricity provided by clean, renewable sources of energy.

Urbanization and Smart Growth: American cities – especially their downtowns – are experiencing a renaissance, driven by a growing desire for walkable living. A future in which most new development takes place in urban and walkable neighborhoods could reduce transportation greenhouse gas emissions by 9 to 15 percent by mid-century, according to research by the Urban Land Institute.

Shared Mobility: Over the last decade, an explosion of technology-enabled services – from carsharing to bikesharing to Lyft and Uber – has revolutionized transportation in many cities. Some of these “shared mobility” services have been shown to reduce vehicle ownership and driving, while the effects of others are just beginning to be studied.

Public Transportation: Transit ridership hit a modern high in 2014, the result of recent transit expansion projects and growing urban population and employment. Current public transportation services reduce vehicle travel (and greenhouse gas emissions) by about 10 percent in U.S. cities, according to research conducted for the Transportation Research Board.

Reallocating Space: The vast majority of street space in American cities is devoted to moving or storing cars, pushing people who walk, bike or take transit to the margins. Cities in the United States and around the world are reallocating space formerly devoted to cars to other public purposes, encouraging the use of low-carbon modes of transportation. U.S. cities with good bicycling infrastructure have nearly twice as many bike commuters as the national average.

Smart Pricing: Americans typically pay nothing to drive on most roads and enjoy the lowest gas taxes in the industrialized world. Government subsidies for driving and parking, along with free access to roads and policies that encourage annual pricing for auto insurance and other costs of driving, create economic signals that encourage Americans to drive and put competing low-carbon transportation modes at an economic disadvantage. Cities around the world have shown that smart pricing policies can reduce congestion and encourage the use of low-carbon modes of travel.

Walking and Biking: Americans prefer walking to any other mode of transportation, according to a recent survey, and the number of people traveling by bicycle in many cities has grown dramatically in the last decade. The Institute for Transportation and Development Policy estimates that bicycling alone could curb global carbon dioxide emissions from transportation by 11 percent by 2050.

Information Technology: Advances in technology are enabling Americans to plan, schedule and pay for trips via low-carbon modes as easily as traveling by car. Real-time transit information has already been shown to trigger modest increases in transit ridership.


Texas Remote Sensing Emission Enforcement (

The state of Texas uses remote sensing along highways to identify high emitters (vehicles with exceptionally high tailpipe emissions). Owners of such vehicles are sent a notice requiring them to have an emission test. During a typical month the program identifies approximately 450 high emitting vehicles. Approximately 70% of those vehicle owners receive a notice. Of those, approximately 60% comply with the testing requirement and, if failing, have the vehicles repaired and retested. A portion of the remaining 40% have their cases forwarded to law enforcement for citation and prosecution. This program has also helped identify emission inspection stations that appear to have performed inaccurate, and possibly fraudulent, tests.


Seattle Climate Action Plan (

In 2005 Seattle Mayor Greg Nickels established a Green Ribbon Commission that included a wide variety of stakeholders and experts to recommend climate protection actions for the Seattle community to meet or beat the Kyoto target. In 2006 the Commission released a report and recommendations, which include the following strategies to reduce automobile use (plus other strategies to reduce emissions in other ways):

·         Increase the Supply of Frequent, Reliable and Convenient Public Transportation

·         Significantly Expand Bicycling and Pedestrian Infrastructure

·         Lead a Regional Partnership to Develop and Implement a Road Pricing System

·         Implement a New Commercial Parking Tax

·         Expand Efforts to Create Compact, Green, Urban Neighborhoods


Along with their recommendations the Commission offered these observations:


·         Success will require a deliberate, sustained, community-wide effort. And, since cars and other transportation sources are the largest source of climate pollution in our area, we will need strong regional collaboration as well.


·         The actions and investments needed to rein in Seattle’s climate pollution will, at the same time, make our community healthier and more livable, for example, by reducing traffic congestion and toxic air pollution from diesel emissions.


·         In addition, reducing our reliance on fossil fuels increases our energy independence, keeps more money circulating in the local economy and supports local and regional economic development.


·         The road to a more climate-friendly community is paved with economic opportunities, including cost-savings from energy efficiency measures for our families and businesses—especially in light of rising and volatile energy prices—and new business prospects for our companies and entrepreneurs.


·         Implementing these recommendations requires a significant investment of time and money by the community. But we believe the price tag is dwarfed by the cost to our community of not taking additional action.


·         Finally, meeting the Kyoto target here—and, more important, transforming Seattle into the nation’s most climate-friendly city—is an extraordinary challenge. But our community has rallied to meet such challenges in the past. With Seattle’s unique mix of eco-intelligence and entrepreneurial zeal, we will meet and exceed the goal.



Visioning and Backcasting for UK Transport Policy (

This research project by the Bartlett School of Planning, University College London involves estimating emission reductions needed to achieve 60% reduction in climate change emissions from baseline by 2030, and evaluates various packages of policies to achieve such reductions, including new technologies and travel reduction incentives. It involved three main stages:

  1. Set targets for 2030 and to forecast the business as usual situation for all forms of transport in the UK over that period, so that the scale of change can be assessed in terms of achieving emission reduction targets.
  2. Describe the transport system in 2030 that will meet the reduction target, considering various combinations of technological and the behavioural options.
  3. Backcaste the effects of various policy packages for achieving emissions reduction targets. This allows policy and planning options to be evaluated.


The analysis indicates that the 60% emission reduction target (in 2030) can be achieved by a combination of behavioural change and technological innovation. Travel behaviour change is particularly important and so should be implemented at the earliest possible occasion. Changes in the built environment will become effective in the medium term (over 10-15 years), whilst the major contribution of technological innovation will only be effective in the period after 2020. It is not possible to achieve the 60% reduction target (in 2030), with the expected growth in travel, as the increase in emissions from this growth outweighs many of the possible savings from behavioural change and technological innovation.



Emission Reductions in Developing Countries (

The Pew Center on Global Climate Change programs has sponsored research on “Transportation in Developing Countries,” which identifies a variety of cost effective strategies for reducing local and global air emissions from motor vehicles in developing country cities. This research recommends various strategies to encourage more efficient vehicles and reduced automobile dependency, including improved facilities for non-motorized transport, use of more efficient motorcycle/scooter engines, improved public transit service, more use of traffic management, and alternative fuels.



Emission Reduction Legislation and Strategies (ETAAC, 2008)

California Assembly Bill AB32 requires the state to reduce greenhouse gases 25% by 2020 and 80% by 2050. A study by the California Economic and Technology Advisory Committee (ETAAC, 2008) identified a number of opportunities to reduce CO2 and other GHG emissions, and discusses their costs, benefits (including cobenefits) and implementation requirements of these strategies.


Moving Cooler (

The report, Moving Cooler: Transportation Strategies to Reduce Greenhouse Gas Emissions (Cambridge Systematics 2009) evaluates several dozen climate change emission reduction strategies, including their emission reductions, implementation costs, impacts on vehicle costs, and equity impacts. It estimates the emissions that could be reduced under a range of assumptions about how they are implemented – from expanding current practice more quickly and broadly to major changes in public policy and regulation. The following categories of impacts are considered.












Urban Transportation Emissions Calculator (

The Urban Transportation Emissions Calculator developed by Transport Canada is a simple, user-friendly tool for estimating annual greenhouse gas (GHG) and criteria air contaminant (CAC) emissions from passenger, commercial, and urban transit vehicles. The primary input to the Tool is vehicle kilometres travelled (VKT) for road vehicles and passenger kilometres travelled (PKT) for rail vehicles. Other inputs relating to average travel speeds, expansion factors, and vehicle fuelling characteristics can be modified from default values.


The Tool estimates GHG and CAC emissions for the following vehicles:



The Tool calculates both the direct and indirect GHG emissions associated with the operation of vehicles. Direct GHG emissions are released directly from the tailpipe of a vehicle. Indirect GHG emissions are created and released from production of electricity used by electric vehicles (i.e. trolleys and light rail) as well as from the production, refining and transportation of transportation fuels (i.e. from wells to pump). It is important to note that the Tool does not address life-cycle emissions associated with the manufacture and end of life recycling of vehicles. Due to the unavailability of appropriate emission factors, only direct CAC emissions are estimated. The Tool also considers the impacts of new technologies and alternative fuels on GHG and CAC emissions based on existing technologies and available data.


The Tool requires the user to select the province of the municipality of interest and the study year. This allows the Tool to account for the varied provincial breakdowns of light-duty passenger vehicles (i.e., proportion of automobiles vs. light trucks) as well as the differing GHG intensities associated with electricity production in each province. It also allows the selection of a modelling year in five year increments from 2006 through 2031 (to correspond with Census years), as vehicle fuel efficiencies and other emission factors are predicted to improve in the future.


Achieving California’s Greenhouse Gas Goals: A Focus on Transportation: A Report for Next 10 (PIEEE 2015)

California has adopted a suite of ambitious policies to reduce carbon emissions from the transportation sector and, in doing so, the state is providing experience and lessons for other jurisdictions that are interested in pursuing similar policies. This report assesses these policies and programs in various ways, including technological feasibility, potential emission reductions and cost effectiveness. It concludes that the state’s 2050 transportation emission reduction goals are achievable, which would provide mobility at lower total costs than the current system and with significant social benefits, but success requires overcoming significant transition costs and non-market barriers. Although most of these policies are in their early stage of implementation and they are generally on track to meet their respective and combined goals, continuous progress evaluation is important.


Evaluation Of Transport Interventions In Developing Countries (Robertson, Jägerbrand and Tschan 2015)

This report investigate the needs and gaps in developing countries’ ability to measure, report and verify the emission reductions of transportation policies and projects. The study reviewed the general and transportation-specific data availability, requirements and methodologies used by national and international organizations for evaluating the emission impacts of transport policies and projects in developing countries. The study concludes that traffic and transportation impact evaluation is a complex and demanding process, and the potential for misinterpretation of results is significant. Other challenges relate to institutional roles and responsibilities, the availability of personal and financial resources, and the knowledge and perspectives applied. Based on these findings the report recommends further development of transport-related climate mechanisms towards a more sectoral and transformational perspective.



Community Travel and Emission Modeling (Frank, et al, 2011)

The study, An Assessment of Urban Form and Pedestrian and Transit Improvements as an Integrated GHG Reduction Strategy, by the Washington State Department of Transportation ( evaluates the effects of various urban form factors on vehicle travel and carbon emissions. It found that increasing sidewalk coverage from a ratio of 0.57 (the equivalent of sidewalk coverage on both sides of 30% of all streets) to 1.4 (coverage on both sides of 70% of all streets) was estimated to result in a 3.4% decrease in VMT and a 4.9% decrease in CO2. Land use mix had a significant association with both CO2 and VMT at the 5 percent level. Parking cost had the strongest associations with both VMT and CO2. An increase in parking charges from approximately $0.28 per hour to $1.19 per hour (50th to 75th percentile), resulted in a 11.5% decrease in VMT and a 9.9% decrease in CO2. However, the required data were only available in more urbanized communities which limited the analysis.


Based on the study results, the research team developed and tested a spreadsheet tool

to estimate the potential reduction in CO2 and VMT due to urban form, sidewalk coverage, transit service and travel cost changes suitable for neighborhood and regional planning. This tool was applied in two Seattle neighborhoods – Bitter Lake and Rainier Beach. Rainier Beach is the location of a new light rail (LRT) stop, while Bitter Lake is along a forthcoming bus rapid transit (BRT) service corridor, and both have a large degree of potential to transition into more walkable, transit supportive areas in the future. The results indicate that current policy will produce small decreases in VMT and CO2: a nearly 8% decrease in VMT, and a 1.65% decrease in CO2 for Bitter Lake; and a 6.75% decrease in VMT and a 2.2% decrease in CO2 for Rainier Beach. This indicates that more investment in pedestrian infrastructure and transit service will almost certainly be needed in order to meet VMT and CO2 reduction targets. A scenario was developed that was focused on VM2 / CO2 reduction – complete sidewalk coverage, decreases in transit travel time and cost, and increases in parking costs, and slight adjustments to the mix of land uses. In total, these changes resulted in a 48% VMT reduction and a 27.5% CO2 reduction for Bitter Lake, and a 27% VMT reduction / 16.5% CO2 reduction for Rainier Beach – substantial departures from the trend that begin to illustrate what might have to happen in order to reach stated goals for VMT reduction.



Emission Calculators

Below are examples of emission calculators.

·         Add Up Your Carbon Dioxide Emissions ( Determines average annual CO2 emissions by filling out a questionnaire. Results tabulate pounds of CO2 produced for each daily activity compared to U.S. average annual emissions.

·         Business Energy Analyzer ( The Business Energy Analzyer is designed to provide a comprehensive analysis of energy use in your business along with customized energy efficiency improvement recommendations. The calculator prepares a report, based on information submitted by the user, showing investments with greatest savings and those with the fastest payback on investment.Information on multiple buildings may be stored and updated for use in future analyses.

·         CarbonCounter ( is an individual carbon dioxide emissions calculator generated by The Climate Trust, a pioneering non-profit organization that invests in high-quality projects that reduce greenhouse gas emissions.

·         Climate Change Calculator ( This tool prepared for the Canadian government calculates personal greenhouse gas emissions and lists mitigation strategies. Using a graphical example of a Canadian community, the user answers a series of questions on home heating and cooling, appliances, transportation and recreation activities. The calculator estimates personal CO2 emissions, offers suggestions for reducing emissions, and shows reductions achieved for those actions. The reporting function provides a graphical emissions breakdown for each feature.

·         Density Effects Calculator ( Indicates how neighborhood density impacts the environment (land, materials, energy and driving).

·         Emissions Calculator ( This emissions calculator tabulates a user's aggregate monthly emissions of seven air pollutants (in pounds) from electricity and natural gas consumption, airplane trips, and vehicle miles traveled (auto or sport utility vehicle/truck) and compares them with average national emissions.

·         Energy Advisor / Home Energy Saver ( The Home Energy Saver is designed to help identify the best ways to save energy in a home. The Home Energy Saver asks for a detailed description of your home, and then quickly computes energy use on-line. Results are provided in dollars, kilowatt hours and CO2 emissions for your house and the most energy efficient house. In addition, the Home Energy Saver's "Making it Happen" and "Energy Librarian" modules connect users to an expanding array of "how-to" information resources throughout the Internet.

·         EPA's Personal Online Greenhouse Gas Calculator (

·         Greenhouse Gas Equivalencies Calculator ( It translates greenhouse gas (GHG) reductions from units that are typically used to report reductions (e.g., metric tons of carbon dioxide equivalent) into terms that are easier to conceptualize.

·         Home Analyzer ( The Home Analyzer is designed to provide a comprehensive analysis of energy use in your home, descriptions of measures to reduce energy use, and comparisons to similar homes. Estimates of monthly and annual energy costs and CO2 emissions are provided for eight categories of home energy use.

·         Home Energy Checkup ( Home Energy Checkup is a guide to identifying options for reducing energy costs through energy efficiency improvements. You can select from among 15 energy efficiency measures, compare costs to your current equipment or materials, and calculate cost and CO2 savings. It includes references to more sophisticated software tools, equipment manufacturers, and other sources of information.

·         How Much Does Your Vehicle Pollute? ( Determines your auto's carbon dioxide, sulfur dioxide, and nitrogen oxide emissions.

·         MetroQuest ( Evaluates the consequences of different long-term planning strategies.

·         Personal CO2 Calculation ( This worksheet determines yearly direct personal carbon dioxide emissions. Results include yearly personal carbon dioxide emissions and a per capita comparison chart to other industrialized countries. Suggestions on reducing emissions and saving money.

·         Personal Environmental Impact Calculator ( Calculates personal environmental impacts from home energy, transportation, recycling habits and water usage. Results include emissions of CO2 sulfur dioxide, nitrogen oxide, nuclear fuel, and particulates.

·         Power Profiler ( The Power Profiler helps users determine the specific air emissions impacts of electricity used to power their home or business using actual monthly energy use information (provided by the user), average monthly use, or default values for monthly residential and commercial electricity use.

·         Recycled Content Tool (  The Recycled Content (ReCon) Tool calculates the GHG emission and energy impacts of increasing the post-consumer recycled content of materials purchased or manufactured.

·         SafeClimate Carbon Dioxide Footprint Calculator (  SafeClimate’s calculator allows individuals in the U.S., Canada and 36 other countries to calculate their "carbon footprint" by tracking residential and transportation energy consumption and greenhouse gas emissions.

·         Tool For Costing Sustainable Community Planning ( by the Canadian Mortgage and Housing Corporation allow a user to estimate the major costs of community development, particularly those that change with different forms of development (e.g., linear infrastructure), and to compare alternative development scenarios.

·         Travel Matters Emissions Calculators ( TravelMatters! from the Center for Neighborhood Technology that provides a trio of resources - interactive emissions calculators, online emissions maps, and a wealth of educational content - that emphasize the relationship between more efficient transit systems and lower greenhouse gas emissions. TM's Emissions Calculator allows users to conceptualize how much carbon dioxide they emit due to their travel decisions. The site also offers transportation emissions by county for all contiguous states.

·         The Zerofootprint Calculator ( enables you to measure and understand the impact of your ecological footprint, taking into account both direct and indirect resource consumption. Zerofootprint Cities is an initiative designed for Mayors of the world's cities to engage their citizens around climate change.

·         ITDP and CAI-Asia Center (2010), Transport Emissions Evaluation Models for Projects (TEEMP), Clean Air Initiative for Asian Cities ( and the Institute for Transportation and Development Policy (; at The Excel-based TEEMP models were developed for evaluating the emissions impacts of ADB's transport projects ( and were modified and extended by ITDP, CAI-Asia and Cambridge Systematics for the for Global Environmental Facility ( Scientific and Technical Advisory Panel (STAP). The Manual for Calculating Greenhouse Gas Benefits of Global Environmental Facility Transportation Projects ( provide step-by-step instructions for developing baseline and impact estimations for various types of transport policies and projects, including transport efficiency improvement, public transport, non-motorized transport, transport demand management, and comprehensive transport strategies.



References and Resources for More Information


AASHTO (2009), Real Transportation Solutions for Greenhouse Gas Emissions Reductions, American Association of State Highway Transportation Officials (; at


ADB (2010), Reducing Carbon Emissions from Transport Projects, Asian Development Bank (; at and


Linda Bailey (2007), Public Transportation and Petroleum Savings in the U.S.: Reducing Dependence on Oil, ICF International for the American Public Transportation Association (; at


Matthew Barth and Kanok Boriboonsomsin (2009), “Traffic Congestion and Greenhouse Gases” Access 35 (, Fall, pp. 2-9; at


Marlon G. Boarnet and Susan Handy (2014), Policy Brief on the Impacts of Residential Density Based on a Review of the Empirical Literature, for Research on Impacts of Transportation and Land Use-Related Policies, California Air Resources Board (


Susanne Böhler-Baedeker and Hanna Hüging (2012), Urban Transport and Energy Efficiency, Module 5h, Sustainable Transportation Sourcebook: A Sourcebook for Policy-Makers in Developing Countries, by the Sustainable Urban Transport Project – Asia (; at


Joel K. Bourne (2007), “Biofuels: Boon or Boondoggle?,” National Geographic, Oct. 2007, pp. 38-59.


C40 Cities (2008), Best Practices: Transport Case Studies, Climate Leadership Group, C40 Cities ( C40 is a group of the world’s largest cities committed to tackling climate change.


CALTRANS (2008), California Transit-Oriented Development (TOD) Searchable Database, California Department of Transportation (


Cambridge Systematics (2009), Moving Cooler: Transportation Strategies to Reduce Greenhouse Gas Emissions (, U.S. Environmental Protection Agency (EPA); Federal Highway Administration (FHWA); Federal Transit Administration (FTA); Intelligent Transportation Society of America (ITSA); Kresge Foundation; Rockefeller Foundation; Shell Oil; Surdna Foundation; Funders Network for Smart Growth; and the Urban Land Institute; summary at


CARB (2010-2011), Research on Impacts of Transportation and Land Use-Related Policies, California Air Resources Board (; at


Carbon Tax Center ( provides information on carbon tax issues.


CCAP (2005), Transportation Emissions Guidebook: Land Use, Transit & Transportation Demand Management, Center of Clean Air Policy ( This Guidebook provides information on various smart growth and mobility management strategies, including rules-of-thumb estimates of VMT and emission reductions. Each part of the guidebook contains a series of policy briefs which include information about each strategy, including an overview, cobenefits, implementation, case studies and information resources. It includes a spreadsheet model that calculates total emission reductions from specific combinations of these strategies.


Mikhail Chester and Arpad Horvath (2008), Environmental Life-cycle Assessment of Passenger Transportation: A Detailed Methodology for Energy, Greenhouse Gas and Criteria Pollutant Inventories of Automobiles, Buses, Light Rail, Heavy Rail and Air v.2, UC Berkeley Center for Future Urban Transport: A Volvo Center of Excellence, Paper vwp-2008-2 (; at


Clean Air Initiative (, by the World Bank is a partnership that advances innovative ways to improve air quality in cities around the world by sharing knowledge and experiences. It includes technical information on transportation emission reduction strategies and policy reforms.


CNT (2010), Transit Oriented Development and The Potential for VMT-related Greenhouse Gas Emissions Growth Reduction, Center for Neighborhood Technology ( for the Center for Transit Oriented Development; at


Rafael Cobian, Tony Henderson, Sudeshna Mitra, Cornelius Nuworsoo and Edward Sullivan (2009), “Vehicle Emissions and Level of Service Standards: Exploratory Analysis of the Effects of Traffic Flow on Vehicle Greenhouse Gas Emissions,” ITE Journal (, Vol. 79, No. 4, April, pp. 30-41.


Randall Crane and John Landis (2010), “Planning for Climate Change: Assessing Progress and Challenges: Introduction to the Special Issue,” Journal of the American Planning Association, Vol. 76, No. 4, pp. 389 – 401.


Todd Davis and Monica Hale (2007), Public Transportation's Contribution to Greenhouse Gas Reduction, American Public Transportation Association (; at


Nathaniel Decker, et al. (2017), Right Type, Right Place: Assessing the Environmental and Economic Impacts of Infill Residential Development through 2030, Terner Center for Housing Innovation, Next 10 (; at


Mark Delucchi (2000), “Environmental Externalities of Motor-Vehicle Use in the US,” Journal of Transportation Economics and Policy, Vol. 34, No. 2, May 2000, pp. 135-168.


Mark A. Delucchi (2003), A Lifecycle Emissions Model (LEM): Lifecycle Emissions from Transportation Fuels, Motor Vehicles, Transportation Modes, Electricity Use, Heating and Cooking Fuels, and Materials, ITS-Davis, Publication No. UCD-ITS-RR-03-17 (


Jennifer Dill (2004), “Scrapping Old Cars,” Access, University of California Transportation Center (, Spring 2004.


Stuart Donovan, et al. (2008), Managing Transport Challenges When Oil Prices Rise, Research Report 357, New Zealand Transport Agency (; at


Pedro Donoso, Francisco Martinez and Christopher Zegras (2006), “The Kyoto Protocol and Sustainable Cities: Potential Use of Clean-Development Mechanism in Structuring Cities for Carbon-Efficient Transportation,” Transportation Research Record 1983, TRB (, pp. 158-166; at


Alan Durning (2008), Sightline's Cap and Trade 101: A Climate Policy Primer, Sightline Institute (; at


Tony Dutzik (2016), 50 Steps Toward Carbon-Free Transportation:  Rethinking U.S. Transportation Policy to Fight Global Warming, Frontier Group (, Environment America Research and Policy Center (; at


EEA (2008), Success Stories Within the Road Transport Sector On Reducing Greenhouse Gas Emission And Producing Ancillary Benefits, European Environment Agency (; at


EIA (annual reports), Annual Energy Review, Energy Information Administration (; at provides information on U.S. energy production, consumption, trade, stocks, and prices.


EIO-LCA Model ( is a computer model that quantifies the economic and environmental impacts of producing goods or services, including total energy consumption and pollution emissions.


EMBARQ (2008), Measuring The Invisible: New EMBARQ Publications Help Cities Quantify Emissions From Reductions From Transport Solutions, EMBARQ - The World Resources Institute Center for Sustainable Transport (; at


Energy Environment Excellence Fleet Management ( provides practical information for optimizing vehicle fleet fuel efficiency and environmental performance.


ETAAC (2008), Technologies and Policies to Consider For Reducing Greenhouse Gas Emissions In California, California Economic and Technology Advancement Advisory Committee for the California Air Resources Board (; at


Reid Ewing, Keith Bartholomew, Steve Winkelman, Jerry Walters and Don Chen (2007), Growing Cooler: The Evidence on Urban Development and Climate Change, Urban Land Institute and Smart Growth America (


Graham Floater and Philipp Rode (2014), Cities and the New Climate Economy: the Transformative Role of Global Urban Growth, NCE Cities – Paper #1,  supporting paper commissioned by the London School of Economics’ LSE Cities program (, for the Global Commission on the Economy and Climate’s New Climate Economy Cities Program  (; at


Fuel Economy Website (, by the U.S. Department of Energy and the U.S. Environmental Agency provides information on fuel consumption ratings of new automobiles and additional information on vehicle efficiency strategies.


FEAT (Fuel Efficiency Automobile Test) Data Center ( provides information on the results of numerous remote sensing vehicle emission studies. This technique is able to measure tailpipe emissions from vehicles as they operate on the roadway.


FHWA (2017), Energy and Emissions Reduction Policy Analysis Tool, Federal Highway Administration (; at This integrated, state-level modeling system evaluates strategies for reducing transportation energy consumption and greenhouse (GHG) emissions.


Lawrence D. Frank, et al. (2011), An Assessment of Urban Form and Pedestrian and Transit Improvements as an Integrated GHG Reduction Strategy, Washington State Department of Transportation (; at


Christopher Frey and Magui Rouphail (2001), Emissions Reductions Through Better Traffic Management: An Empirical Evaluation Based on On-Road Measurements, North Carolina State University and North Carolina Dept. of Transportation (


Frank Gallivan, et al. (2015), Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component, Report 176, Transit Cooperative Research Program (; at


GEF (2006), Environmentally Sustainable Transport and Climate Change: Experiences and Lessons from Community Initiatives; The Global Environment Facility, United Nations Environment Programme (; at


GHG Assessment Tools ( describes various methods used to quantify transport sector greenhouse gas emissions, and the impacts of emission reduction strategies.


Edward L. Glaeser and Matthew E. Kahn (2008), The Greenness Of Cities: Carbon Dioxide Emissions And Urban Development, Working Paper 14238, National Bureau Of Economic Research; at; summarized in


Global Commission on Environment and Economy (2014), Better Growth, Better Climate: The New Climate Economy Report, Global Commission on the Economy and Climate (; at


David Goldstein (2007), Saving Energy, Growing Jobs: How Environmental Protection Promotes Economic Growth, Profitability, Innovation, and Competition, Bay Tree Publishers (


V. Gorsevski, et al (1998), Air Pollution Prevention Through Urban Heat Island Mitigation: An Update on the Urban Heat Island Pilot Project, Global Hydrology and Climate Center (


Michael Grant, Anne Choate and Lauren Pederson (2008), Assessment of Greenhouse Gas Analysis Techniques for Transportation Projects, Transportation Research Board 87th Annual Meeting (; at


Michael Grant, et al. (2013), A Performance-Based Approach to Addressing Greenhouse Gas Emissions through Transportation Planning, FHWA-HEP-14-020, Federal Highway Administration (; at


David L. Greene and John DeCicco (2000), Engineering-Economic Analysis of Automotive Fuel Economy Potential in the United States, Oak Ridge National Laboratory (ORNL-27, 3-96).


GTZ (2003), Sustainable Transportation: A Sourcebook for Policy-Makers in Developing Countries, (, by the Sustainable Urban Transport Project – Asia ( and Deutsche Gesellschaft fur Technische Zusammenarbeit ( Users are required to register, but there is no charge and the documents may be downloaded free. Many of these documents are now available in various languages including Spanish, French, Chinese, Indonesian, Romanian, Thai and Vietnamese. The Mobility Management module is available at the VTPI website ( Preserving and Expanding the Role of Non-motorized Transport: Sustainable Transportation is available at the Institute for Transportation and Development Policy website (


Greig Harvey and Elizabeth Deakin (1998), “The STEP Analysis Package: Description and Application Examples,” Appendix B, in Technical Methods for Analyzing Pricing Measures to Reduce Transportation Emissions, USEPA Report #231-R-98-006, (


Moazzem Hossain and Scott Kennedy (2008), ‘Estimating Energy Savings from Bus Improvement Options in Urban Corridors,’ Journal of Public Transportation, Vol. 11, No. 3, (, pp. 19-40.


ICF International (2008), The Broader Connection Between Public Transportation, Energy Conservation and Greenhouse Gas Reduction, American Public Transportation Association (


ICF International (2011), Potential Changes in Emissions Due to Improvements in Travel Efficiency, Contract No. EP-C-06-094, Transportation and Regional Programs Division, U.S. Environmental Protection Agency (; at


IEA (2005), Saving Oil in a Hurry, International Energy Agency (; at Also see Managing Oil Demand In Transport, International Energy Agency (; at


IGES (2008), Climate Change Policies in the Asia-Pacific: Re-Uniting Climate Change and Sustainable Development, Institute for Global Environmental Strategies (


International Institute for Energy Conservation ( works to implement sustainable energy in developing and transition countries.


International Council on Clean Transportation ( works to dramatically improve the environmental performance and efficiency of motor vehicles and transportation systems.


ITDP (2010), Manual for Calculating Greenhouse Gas Benefits of Global Environmental Facility Transportation Projects, Institute for Transportation and Development Policy, for the Scientific and Technical Advisory Panel of the Global Environment Facility (; at


ITE Climate Change and Energy Task Website ( by the Institute of Transportation Engineers provides information on transportation emissions, emission reduction and mitigation strategies.


Christopher M. Jones, Stephen M. Wheeler and Daniel M. Kammen (2018), “Carbon Footprint Planning: Quantifying Local and State Mitigation Opportunities for 700 California Cities,” Urban Planning (ISSN: 2183–7635), Vol. 3, Is. 2, (DOI: 10.17645/up.v3i2.1218).


JRC (2011), Location Efficiency and Housing Type—Boiling it Down to BTUs, Jonathan Rose Companies for the U.S. Environmental Protection Agency (; at


Jeff Kenworthy (2007), “Urban Planning and Transport Paradigm Shifts For Cities For The Post-Petroleum Age,” Journal of Urban Technology (, Vol. 14, No. 2, August 2007, pp. 47-70.


Kara M. Kockelman, Matthew Bomberg, Mellisa Thompson and Charlotte Whitehead (2009), GHG Emissions Control Options: Opportunities for Conservation, for the Committee on the Relationships Among Development Patterns, Vehicle Miles Traveled, and Energy Consumption; for Special Report 298, Driving And The Built Environment: The Effects Of Compact Development On Motorized Travel, Energy Use, And CO2 Emissions, Transportation Research Board (; at


Doug Koplow (2006), Government Support For Ethanol And Biodiesel In The United States Biofuels – At What Cost?, Global Subsidies Initiative, International Institute for Sustainable Development ( 


Doug Koplow (2010), G20 Fossil-Fuel Subsidy Phase Out: A Review of Current Gaps and Needed Changes to Achieve Success, EarthTrack (; at


Lawrence Frank and Company, Inc., Mark Bradley and Keith Lawton Associates (2005), Travel Behavior, Emissions, & Land Use Correlation Analysis In The Central Puget Sound, Washington State Transportation Commission, Department of Transportation, in cooperation with the U.S. Department of Transportation and the Federal Highway Administration; at


Tara Laan, Todd Litman and Ronald Steenblik (2009), Biofuels – At What Cost? Government Support For Ethanol And Biodiesel In Canada, International Institute for Sustainable Development (; at


Kathleen Leotta (2007), Implementing the Most Effective TDM Strategies to Quickly Reduce Oil Consumption, Henry L. Michel Fellowship Program, PB, Post Carbon Cities (; at


Shanjun Li, Joshua Linn and Elisheba Spiller (2011), Evaluating “Cash-for-Clunkers” Program Effects on Auto Sales and the Environment, Resources for the Future (; at


Todd Litman (2001), “Generated Traffic; Implications for Transport Planning,” ITE Journal, Vol. 71, No. 4, Institute of Transportation Engineers (, April, 2001, pp. 38-47; at


Todd Litman (2004), Evaluating Mobility Management Strategies for Reducing Transportation Emissions in the Fraser River Basin, Victoria Transport Policy Institute (; at; spreadsheet at


Todd Litman (2005), “Efficient Vehicles Versus Efficient Transportation: Comparing Transportation Energy Conservation Strategies,” Transport Policy, Volume 12, Issue 2, March, Pages 121-129; at


Todd Litman (2006), Win-Win Transportation Emission Reduction Strategies, Victoria Transport Policy Institute (; at


Todd Litman (2007), Win-Win Transportation Solutions, Victoria Transport Policy Institute (; at


Todd Litman (2008), Smart Transportation Emission Reduction Strategies, Victoria Transport Policy Institute (; at


Todd Litman (2008), Appropriate Response To Rising Fuel Prices, Victoria Transport Policy Institute (; at


Todd Litman (2008), Recommendations for Improving LEED Transportation and Parking Credits, VTPI (; at


Todd Litman (2009), Transportation Cost and Benefit Analysis; Techniques, Estimates and Implications, Victoria Transport Policy Institute ( Includes chapters on “Air Pollution Costs” ( and “Resource Consumption External Costs” (


Todd Litman (2009), Climate Change Emission Valuation for Transportation Economic Analysis, Victoria Transport Policy Institute (; at


Todd Litman (2009), Are Vehicle Travel Reduction Targets Justified? Evaluating Mobility Management Policy Objectives Such As Targets To Reduce VMT And Increase Use Of Alternative Modes, Victoria Transport Policy Institute (; at


Todd Litman (2009), “Evaluating Carbon Taxes as an Energy Conservation and Emission Reduction Strategy,” Transportation Research Record 2139, Transportation Research Board (, pp. 125-132; based on Carbon Taxes: Tax What You Burn, Not What You Earn, Victoria Transport Policy Institute (; at


Todd Litman (2011), Evaluating Public Transit as An Energy Conservation and Emission Reduction Strategy, presented at Aligning Environmental and Transportation Policies To Mitigate Climate Change Institute for Policy Integrity, 26 October 2011, New York University School of Law (; at


Todd Litman (2011b), “Can Smart Growth Policies Conserve Energy and Reduce Emissions?” Portland State University’s Center for Real Estate Quarterly  (, Vol. 5, No. 2, Spring, pp. 21-30; at


Todd Litman (2011c), Critique of the National Association of Home Builders’ Research On Land Use Emission Reduction Impacts, Victoria Transport Policy Institute (; at


Todd Litman (2013), “Comprehensive Evaluation of Energy Conservation and Emission Reduction Policies,” Transportation Research A, Vol. 47, January, pp. 153-166 (; at


Todd Litman (2013), “Full Cost Analysis of Petroleum,” Transportation Beyond Oil: Policy Choices for a Multimodal Future, (John Renne and Billy Fields, eds), Island Press (; at


Todd Litman (2014), Economically Optimal Transport Prices and Markets: What Would Happen If Rational Policies Prevailed? paper 11, presented at the International Transportation Economic Development Conference (; at Also see, Socially Optimal Transport Prices and Markets, Victoria Transport Policy Institute (; at


Todd Litman (2015), Analysis of Public Policies that Unintentionally Encourage and Subsidize Sprawl, in partnership with the LSE Cities ( program for the New Climate Economy (; at


Marcelo Maciel, Luiz Rosa, Fernando Correa and Ursula Maruyama (2012), “Energy, Pollutant Emissions and Other Negative Externality Savings from Curbing Individual Motorized Transportation (IMT): A Low Cost, Low Technology Scenario Analysis in Brazilian Urban Areas,” Energies, Vol. 5, pp. 835-861, doi:10.3390/en5030835; at


Julian D. Marshall, Michael Brauer and Lawrence D. Frank (2009), “Healthy Neighborhoods: Walkability and Air Pollution,” Environmental Health Perspectives, Vol. 117, No. 11, pp. 1752–1759;


Mayors Climate Protection Center (, by the U.S. Conference of Mayors, provides information on practical municipal policies and programs that reduce climate emissions.


Gordon McGranahan and Frank Murray (eds.) (2003), Air Pollution & Health in Rapidly Developing Countries, Earthscan (


McKinsey (2007), Reducing U.S. Greenhouse Gas Emissions - How Much at What Cost - US Greenhouse Gas Abatement Mapping Project, McKinsey & Company (; at


MDNR (2005), Gateway Clean Air Program Annual Report, Missouri Department of Natural Resources, Air and Land Protection Division, Air Pollution Control Program (


Michael Mehaffy, Stuart Cowan and Diana Urge-Vorsatz (2009), Factors of Urban Morphology in Greenhouse Gas Emissions:  A Research Overview, presented at the International Alliance of Research Universities Scientific Congress on Climate Change, 10 March; at


Michael West Mehaffy (2015), Urban Form and Greenhouse Gas Emissions Findings, Strategies, and Design Decision Support Technologies, Delft University of Technology (; at


L. Michaelis (1996), Policies and Measures for Common Action – Sustainable Transport Policies: CO2 Emissions from Road Vehicles; Annex I Expert Group on UN FCCC Working Paper 1, OECD (


MJB&A (2014), Comparison of Energy Use & CO2 Emissions from Different Transportation Modes, American Motor Coach Association (; at


W. Ross Morrow, Kelly Sims Gallagher, Gustavo Collantes and Henry Lee (2010), Analysis of Policies to Reduce Oil Consumption and Greenhouse-Gas Emissions from the U.S. Transportation Sector, Belfer Center, Kennedy School of Government, Harvard University (; at


MRC, et al. (2008), Managing Transport Challenges When Oil Prices Rise, Research Report 357, New Zealand Transport Agency (; at


Anne Arquit Neiderberger (2005), “The Swiss Climate Penny: An Innovative Approach to Transport Sector Emissions,” Transport Policy, Vol. 12, No. 4 (, July 2005, pp. 303-313.


Nelson/Nygaard (2005), Crediting Low-Traffic Developments: Adjusting Site-Level Vehicle Trip Generation Using URBEMIS, Urban Emissions Model, California Air Districts (


Robert Noland and Mohammed A. Quddus (2006), “Flow Improvements and Vehicle Emissions: Effects of Trip Generation and Emission Control Technology,” Transportation Research D, Vol. 11 (, pp. 1-14; also see


NZTA (2011), Determination of Personal Exposure to Traffic Pollution While Travelling by Different Modes, The New Zealand Transport Agency (; at


OECD/IEA (2001), Saving Oil and Reducing CO2 Emissions in Transport: Options & Strategies, Organization for Economic Cooperation and Development ( and the International Energy Agency ( 


OECD (2002), Policy Instruments For Achieving Environmentally Sustainable Transport: Report On Phase III Of The Project On Environmentally Sustainable Transport, Working Party on National Environmental Policy, Working Group on Transport, OECD (, 2002.


OECD (2006), Cutting Transport CO2 Emissions: What Progress? Organization for Economic Cooperation and Development (


OECD/ITF (2008), The Cost and Effectiveness of Policies to Reduce Vehicle Emissions, Discussion Paper 2008-9, OECD and International Transport Forum (; at


ORNL (annual reports), Transportation Energy Book, Oak Ridge National Laboratories, U.S. Department of Energy (


Theodore Petritsch, et al. (2008), Energy Savings from Provision of Bicycle Facilities, Transportation Research Board 87th Annual Meeting (


PIEEE (2015), "Achieving California’s Greenhouse Gas Goals: A Focus on Transportation: A Report for Next 10, Policy Institute for Energy, Environment and the Economy, University of California (; at


PPMC (2016), An Actionable Vision of Transport Decarbonization: Implementing the Paris Agreement in a Global Roadmap Aiming At Net-Zero Emissions Transport, Paris Process On Mobility And Climate (PPMC) On Behalf Of The Global Climate Action Agenda Transport Team (; at


Richard H. Pratt (1999-2007), Traveler Response to Transportation System Changes, TCRP Report 95 Series, Web Document 12 (


Kilian Reiche and Witold Teplitz (2009), Energy Subsidies: Why, When and How?, Deutsche Gesellschaft für Internationale Zusammenarbeit (; at


John L. Renne and Billy Fields (2013), Transport Beyond Oil: Policy Choices for a Multimodal Future, (Renne and Fields, eds), Island Press (; at


Michael A. Replogle and Lewis M. Fulton (2014), A Global High Shift Scenario: Impacts And Potential For More Public Transport, Walking, And Cycling With Lower Car Use, Institute for Transportation and Development Policy (; at


Kerstin Robertson, Annika K. Jägerbrand and Georg F. Tschan (2015), Evaluation of Transport Interventions in Developing Countries, Report 855A, VTI (; at


Robert Salter, Subash Dhar and Peter Newman (2011), Technologies for Climate Change Mitigation: Transport Sector, Risø Centre on Energy, Climate and Sustainable Development, United Nations Environmental Program (; at


Andrea Sarzynski, Marilyn A. Brown and Frank Southworth (2008), Shrinking the Carbon Footprint of Metropolitan America: Energy Security, Energy Security, Transportation, Global Warming, Climate Change, Brookings Institution (; at


Maureen Sevigny (1998), Taxing Automobile Emissions for Pollution Control, New Horizons in Environmental Economics, Edward Elgar (


Robert Shapiro, Nam Pham and Arun Malik (2008), Addressing Climate Change Without Impairing the U.S. Economy: The Economics and Environmental Science of Combining a Carbon-Based Tax and Tax Relief, The U.S. Climate Task Force (; at


Sierra Club (2005), Healthy Growth Calculator, Sierra Club ( Calculates household energy consumption and pollution emissions based on housing location and vehicle type.


Michael Sivak and Brandon Schoettle (2011), Eco-Driving:  Strategic, Tactical, and Operational Decisions of the Driver that Improve Vehicle Fuel Economy, University of Michigan Transportation Research Institute (; at


Daniel Sperling (1995), “Prospects for Neighborhood Electric Vehicles,” Transportation Research Record 1444, TRB (, p. 16-22.


Frederik Strompen, Todd Litman and Daniel Bongardt (2012), Reducing Carbon Emissions Through TDM Strategies - A Review of International Examples, Transportation Demand Management in Beijing ( GIZ and the Beijing Transportation Research Centre; at; summary at


SHARP (2011), Practitioner’s Guide to Incorporating Greenhouse Gas Emissions into the Collaborative Decision-Making Framework, Strategic Highway Research Program 2,  

Transportation Research Board (; at


Sir Nicholas Stern (2006), Stern Review on the Economics of Climate Change, HM Treasury (


Surface Transportation Environment and Planning Cooperative Research Program ( provides research information in the area of Planning, Environment and Land Use.


Suzuki (1998), Canadian Solutions: Practical and Affordable Steps to Fighting Climate Change, David Suzuki Foundation and the Pembina Institute for Appropriate Technology (


TCRP (2009), Public Transportation’s Role in Addressing Global Climate Change, Research Results Digest 89, Transportation Research Board (; at


Miles R. Tight, Alison Vicat, Abigail L. Bristow, Alison Pridmore and Anthony D. May (2007), “An Exploration of Household Response To Personal Travel Carbon-Reduction Targets,” International Journal of Sustainable Transportation, Vol. 1, No. 3 (, July-Sept 2007, pp. 143-159.


TØI (2009), Does Road Improvement Decrease Greenhouse Gas Emissions?, Institute of Transport Economics (TØI) of the Norwegian Centre for Transport Research (; English summary at


TransForm (2009), Windfall For All: How Connected, Convenient Neighborhoods Can Protect Our Climate and Safeguard California’s Economy, TransForm (; at


TRB (2009), Driving and the Built Environment: The Effects of Compact Development on Motorized Travel, Energy Use, and CO2 Emissions, Special Report 298, Transportation Research Board (; at


TRB (2011), Policy Options for Reducing Energy Use and Greenhouse Gas Emissions from U.S. Transportation, Special Report 307, Transportation Research Board (; at


TREMOVE ( is a transport and emissions simulation model designed to study the effects of different transport and environment policies on transport sector emissions. It estimates the transport demand, the modal split, the vehicle fleets, the emissions of air pollutants and the welfare level under different policy scenarios.


UITP (2007), A Low Carbon Future With Public Transport, International Association of Public Transport (; at


UKERC (2009), What Policies Are Effective At Reducing Carbon Emissions From Surface Passenger Transport? A Review Of Interventions To Encourage Behaviroual And Technological Change, UK Energy Research Centre; at


ULI (2010), Land Use and Driving: The Role Compact Development Can Play in Reducing Greenhouse Gas Emissions, Urban Land Institute (; at


UN (2016), Mobilizing Sustainable Transport for Development: Analysis and Policy Recommendations from the United Nations Secretary-General's High-Level Advisory Group on Sustainable Transport, United Nations (; at


UNEP (2011), Technologies for Climate Change Mitigation – Transport Sector, Risoe Centre ( for the United Nations Environmental Program; at


USDOE (annual reports), Transportation Energy Data Book, Center for Transportation Analysis, Oak Ridge National Laboratory, US Department of Energy, (


USDOE (2013), Transportation Energy Futures, U.S. Department of Energy (; at


USDOT (2010), Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1, Report to Congress, U.S. Department of Transportation (, at


USEPA (2006), Policy and Guidance: Transportation-Related Documents, Office of Transportation and Air Quality, USEPA (


USEPA, Voluntary Emission Reduction Policies and Programs, U.S. Environmental Protection Agency ( This website describes the successful implementation of various voluntary mobile source reduction measures.


USEPA (2007), Measuring the Air Quality and Transportation Impacts of Infill Development, USEPA (; at


Arthur Winer, Yifang Zhu and Suzanne Paulson (2014), “Carmageddon or Carmaheaven? Air Quality Results of a Freeway Closure,” Access 44, Spring, pp. 10-16; at


WHO (2011), Health Co-Benefits Of Climate Change Mitigation - Transport Sector: Health In The Green Economy, World Health Organization (; at


Lloyd Wright and Lewis Fulton (2005), “Climate Change Mitigation and Transport in Developing Nations,” Transport Reviews (, Vol. 25, No. 6, November 2005, pp. 691–717.

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This Encyclopedia is produced by the Victoria Transport Policy Institute to help improve understanding of Transportation Demand Management. It is an ongoing project. Please send us your comments and suggestions for improvement.




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