Energy Conservation and Emission Reduction Strategies
~~~~~~~~~~~~~~
Victoria Transport Policy Institute
~~~~~~~~~~~~~~~~~~~~
Updated
24 November 2008
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.
Factors Affecting Vehicle Energy Consumption, Emissions
and Exposure
Comparing Clean Vehicle and TDM Strategies
Pay-As-You-Drive Vehicle Insurance and Other Distance
Based Fees
Land Use Management Strategies
Nonmotorized Transportation Improvements and
Encouragement
Transit Improvements and Incentives
High Occupant Vehicle (HOV) Priority
Parking Management and Parking Pricing
Traffic Calming and Roundabouts
Car-Free Planning and Vehicle Restrictions
Sustainable Transportation Planning
Promote Efficient and Low Emission Vehicle Purchases
Efficiency-Based Annual Registration Fees
Transit Emission Reduction Programs
Super-Efficient and Alternative Fuel Vehicle Incentives
Low and Zero Emission Vehicle Mandates
Inspection and Maintenance (I/M) Programs
Roadside “High Emitter” Identification
Fleet Management and Driver Training
Summary of Emission Reduction Strategies
Congestion-Reduction Strategies
Road Capacity Expansion and Traffic Signal
Synchronization
Intelligent Transportation Systems
Evaluating Energy Conservation and Emission Reduction
Strategies
Efficient Vehicles Versus Efficient Transportation
Vacaville Becomes Voltageville With Electric Vehicle
Implementation
Minimize the Air Pollution from Your Consumer Choices
with AirHead.org (http://www.AirHead.org)
Other Cities Follow Lead of New York Buses, Without
Choking
Trees for Travel (www.treesftf.org/travel.htm)
Emission Prices Are More Efficient than Emission Caps
Texas Remote Sensing Emission Enforcement
(www.txdps.state.tx.us/vi)
Seattle Climate Action Plan
(www.ci.seattle.wa.us/climate/report.htm)
Visioning and Backcasting for UK Transport Policy
(www.ucl.ac.uk/~ucft696/vibat2.html)
Emission Reductions in Developing Countries
(www.pewclimate.org)
Emission Reduction Legislation and Strategies (ETAAC,
2008)
Urban Transportation Emissions Calculator
(www.tc.gc.ca/UTEC)
Emission Reduction Legislation (Committee on Energy and
Commerce, 2008)
References And Resources For More Information
Introduction
Motor vehicles are major energy consumers and sources of
air, noise and water pollution. Transportation represents about 27% of total
Table 1 Vehicle
Energy Use (ORNL,
2001, Table 2.5)
|
|
Trillion BTUs |
Percent of Total |
|
Automobiles |
9,126 |
34% |
|
Light Trucks (including vans and SUVs) |
6,617 |
25% |
|
Trucks & Private Buses |
4,563 |
17% |
|
Aviation |
2,546 |
10% |
|
Water |
1,300 |
4.9% |
|
Pipeline |
1,009 |
3.8% |
|
Off-highway (construction and agriculture) |
680 |
2.5% |
|
Railroads |
607 |
2.3% |
|
Buses |
207 |
0.8% |
|
Motorcycles |
26 |
0.1% |
Detailed information on vehicle energy consumption and emissions is available from:
· Transportation Cost and Benefit Analysis Guidebook (www.vtpi.org/tca), includes chapters on air, noise and water pollution, and resource consumption external costs.
· Transportation Air Quality Center, USEPA (www.epa.gov/otaq) provides information on vehicle emissions and emission reduction strategies.
·
Transportation Energy Data Book, ORNL (www.ott.doe.gov) provides information on
· Annual Energy Review, Energy Information Administration (www.eia.doe.gov/emeu/aer/contents.html) provides information on energy production, consumption and prices.
· European Environment Agency (www.eea.eu.int) provides international information on vehicle energy consumption and emissions.
· Office of Transportation And Air Quality Modeling Tools, USEPA (www.epa.gov/otaq/transp/traqmodl.htm) has tools for evaluating the emission reduction impacts of TDM strategies.
· The Green Vehicle Guide, USEPA (www.epa.gov/autoemissions) reports emissions and fuel consumption rates per vehicle mile for specific model years.
· For My World Tailpipe Tally (http://209.10.107.169/tailpipetally_v2/index.cfm?synd=fmw) provides motor vehicle fuel consumption, fuel cost and pollution emissions for specific model-years.
· The Climate Change Cost Calculator (www.climcalc.net/eng/CCCframes.htm) 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 (www.vtpi.org/tca/tca0510.pdf), 2002.
· The Zerofootprint Calculator (www.zerofootprint.net) 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 www.vtpi.org/tca). 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, 2001)
|
Emission |
Description |
Source |
Harmful Effects |
Scale |
|
Carbon monoxide (CO) |
A toxic gas, undermines blood’s ability to carry oxygen. |
Engine |
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 |
Local |
|
Nitrogen oxides (NOx) |
A variety of compounds, some of which are toxic, and all of which contribute to ozone. |
Engine |
Human health, ozone precursor. |
Regional |
|
Hydrocarbons (HC) |
Unburned fuel. Forms ozone. |
Fuel production and engines. |
Human health, ozone precursor. |
Regional |
|
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. |
Regional |
|
Sulfur oxides (SOx) |
Lung irritant, and causes acid rain. |
Diesel engines |
Human health risks, acid rain |
Regional |
|
Carbon dioxide (CO2) |
A byproduct of combustion. |
Fuel production and engines. |
Climate change |
Global |
|
Methane (CH4) |
A gas with significant greenhouse gas properties. |
Fuel production and engines. |
Climate change |
Global |
|
CFC |
Durable chemical widely used for industrial purposes, now banned due to environmental risks. |
Vehicle (especially older air conditioners). |
Ozone depletion |
Global |
|
Noise pollution |
Undesirable noise produced by vehicles. |
Engine, tires, wind |
Aesthetic, distraction, reduced property values. |
Local |
|
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; Delucchi, 2000; Litman, 2001; Stern, 2006).
Delucchi (2000) estimates that
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 (www.urbemis.com) can be used to
predict the emission reduction effects of various mobility management and smart
growth strategies (Nelson/Nygaard, 2005). The
USDOT’s Center
for Climate Change and Environmental Forecasting (http://climate.volpe.dot.gov/about.html)
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 (USEPA, 2002; 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
Table 3 Average Fuel Consumption 2001 (BTS, Tables 1-29, 4-20,
4-23, 4-24; APTA, 2002)
|
Vehicle Class |
Average MPG |
Mode |
BTU/Pass. Mile |
|
Passenger Cars |
22.1 |
Car |
3,578 |
|
Vans, Pickup Trucks, SUVs |
17.6 |
Vans, Pickup Trucks, SUVs |
4,495 |
|
Motorcycle |
50 |
Aviation |
4,000 |
|
Single Unit Truck |
7.4 |
Transit, Bus |
3,697 |
|
Combination Truck |
5.3 |
Transit, Electric Light Rail |
1,152 |
|
Buses (all types) |
6.9 |
Intercity Rail, diesel |
2,134 |
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)
|
Mode |
Embodied |
Fuel |
Total |
|
Urban |
|
|
|
|
Light Rail |
0.7 |
1.4 |
2.1 |
|
Bus |
0.7 |
2.1 |
2.8 |
|
Ferry |
1.2 |
4.3 |
5.5 |
|
Bicycle |
0.5 |
0.3 |
0.8 |
|
Heavy Rail |
0.9 |
1.9 |
2.8 |
|
Car, Petrol |
1.4 |
3.0 |
4.4 |
|
Car, Diesel |
1.4 |
3.3 |
4.8 |
|
Car, LPG |
1.4 |
3.4 |
4.8 |
|
Private Bus |
0.5 |
1.2 |
1.7 |
|
Non-Urban |
|
|
|
|
Bus |
0.3 |
1.0 |
1.3 |
|
Rail |
0.7 |
1.2 |
1.9 |
|
Private Air |
12.4 |
6.5 |
18.9 |
|
Carter Air |
9.1 |
8.7 |
17.8 |
|
Regional Air |
5.4 |
4.3 |
9.7 |
|
Domestic Air |
2.7 |
3.1 |
5.7 |
|
International Air |
0.9 |
2.2 |
3.1 |
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. Actual carbon monoxide and hydrocarbon emissions tend to be significantly higher than what standards allow (DeCicco and Delucchi, 1997).
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 (www.hypercar.com), 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)
|
Type |
Drive System |
Seats |
City |
Highway |
Overall |
|
Average SUV |
Gasoline |
4-6 |
13.8 |
9.3 |
11.8 |
|
Average Car |
Gasoline |
4-5 |
10.1 |
6.3 |
8.4 |
|
|
Hybrid-Gasoline |
4 |
4.6 |
5.3 |
5.1 |
|
Honda Insight |
Hybrid-Gasoline |
2 |
3.9 |
3.5 |
3.6 |
|
Lupo 3L |
Diesel |
2 or 4 |
3.7 |
2.8 |
3.1 |
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 (www.afdc.doe.gov), the Clean Cities website (www.ccities.doe.gov), and the Centre for Alternative Transportation Fuels (http://catf.bcresearch.com). The US Department of Energy’s Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model (www.fleets.doe.gov) calculated the lifecycle emission impacts of alternative fuels (also see Delucchi, 2003).
Table 6 Alternative
Fuels Compared (Pilorusso
Research, 1995; Alternative Fuels Data Center; Pickrell)
|
Fuel |
CO2* |
Advantages |
Disadvantages |
|
Diesel |
20% |
Widely available and used. Reduces carbon emissions. |
Increases emissions of particulates, sulfur and noise. |
|
LPG |
10% |
Increased efficiency and reduced emissions. |
Requires rebuilding engines. Limited availability. |
|
CNG |
20% |
Increased efficiency and reduced emissions. |
Requires rebuilding engines. Limited availability. May reduce methane. |
|
Methanol |
60% |
Reduces some emissions. |
Poisonous. Increases some emissions. |
|
Ethanol |
0-60% |
Reduces some emissions. |
Increases some emissions. Energy savings depend on fuel source. |
|
Electricity |
20-70% |
No tailpipe emissions. May be generated from renewable sources. |
Reduced vehicle performance. Vehicles are currently expensive. Energy savings depend on how electricity is generated. |
|
Hydrogen |
20-70% |
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 (Pickrell, 2003; 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 (USEPA, 2000). 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).
Exposure
Several studies indicate that automobile occupants are
exposed to more harmful air pollution than people traveling by other modes
(Chertok et al, 2004). Air pollution costs (per ton of emission) are higher
where population densities are high, and in areas where geographic and climatic
conditions trap polluted air and produce ozone. Emissions in areas such as
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
Table 7 Summary of Emission Reduction Strategies
|
Clean Vehicles (Reduce Emission Rates) |
TDM (Reduce Vehicle Travel) |
|
Anti-Idling Emission-Based Annual Registration Fees Emission Standards Feebates 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 Ridesharing Road Pricing Speed Reductions TDM Marketing TDM Programs Telework 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 (CCAP, 2003) identifies the following major categories of TDM implementation policies:
- Shift funding toward
more efficient options (Least Cost Planning).
- Promote Location Efficient Development.
- Encourage the use of
more efficient options (TDM Marketing).
- Develop diverse Freight networks.
- Create efficient
options for intercity travel.
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, 2002; CBO, 2002). 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 (USEPA, 1998; Sevigny, 1998). 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)
|
Region |
Fee Basis |
VMT |
Trips |
Delay |
Fuel |
ROG |
Revenue |
|
|
Vehicle Model |
-2.2% |
-1.9% |
-3.5% |
-3.9% |
-5.4% |
$384 |
|
Bay Area |
Vehicle Use |
-1.6% |
-1.4% |
-2.5% |
-6.6% |
-17.7% |
$341 |
|
|
Vehicle Model |
-2.6% |
-2.3% |
-4.5% |
-4.0% |
-5.7% |
$116 |
|
|
Vehicle Use |
-2.3% |
-2.1% |
-5.0% |
-7.4% |
-20.2% |
$102 |
|
|
Vehicle Model |
-2.5% |
-2.2% |
-3.5% |
-4.1% |
-5.5% |
$211 |
|
|
Vehicle Use |
-1.9% |
-1.7% |
-3.5% |
-7.1% |
-19.5% |
$186 |
|
|
Vehicle Model |
-2.5% |
-2.3% |
-5.5% |
-3.9% |
-5.5% |
$1,106 |
|
|
Vehicle Use |
-2.1% |
-1.9% |
-6.0% |
-7.2% |
-18.9% |
$980 |
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. 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)
|
Region |
Tax Increase |
VMT |
Trips |
Delay |
Fuel |
ROG |
Revenue |
|
|
$0.50 |
- 3.6% |
-3.4% |
-8.5% |
-8.8% |
3.5% |
$1,332 |
|
Bay Area |
$2.00 |
-11.7% |
-11.3% |
-25.5% |
-30.6% |
11.6% |
$4,053 |
|
|
$0.50 |
-4.1% |
-3.9% |
-7.0% |
-9.3% |
4.0% |
$414 |
|
|
$2.00 |
-13.2% |
-12.7% |
-22.0% |
-31.8% |
13.0% |
$1,245 |
|
|
$0.50 |
-3.9% |
-3.5% |
-8.0% |
-9.1% |
3.8% |
$747 |
|
|
$2.00 |
-12.5% |
-12.0% |
-23.0% |
-31.1% |
12.3% |
$2,257 |
|
|
$0.50 |
-4.2% |
-3.5% |
-9.5% |
-9.3% |
4.1% |
$3,724 |
|
|
$2.00 |
-13.0% |
-12.5% |
-28.5% |
-31.6% |
12.8% |
$11,235 |
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
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 (www.fuelmasterlogistics.co.uk):
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. One study estimates the price elasticity of aviation fuel at –0.1 in the short run and –0.3 over the long run (Hagler Bailly, 1999). 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 |
Scope |
Travel Affected |
|
Employees in a particular
business or jurisdiction. |
Commute trips (about 25% of
personal travel). |
|
|
Employees, businesses and
clients in a district or jurisdiction. |
Personal and some freight
travel within an area. |
|
|
Serves students, staff and
visitors in a college, university or research campus. |
Commutes, and sometimes
other trips. |
|
|
Serves students, parents
and staff within a school. |
School trips (about 5% of
personal travel). |
|
|
Businesses, employees,
residents and visitors within a district or jurisdiction. |
Travel in the affected
area. |
|
|
Visitors, businesses and
staff. |
Travel in resort areas. Any
leisure travel. |
|
|
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).
· Parking Management and Parking Pricing.
· Alternative Scheduling (Flextime and Compressed Work Weeks).
· TDM Marketing and Promotion.
· 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 (USEPA, 2001; BTRE, 2002; CBO, 2006). 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 (Litman, Komanoff and Howell, 1998), plus additional long-term travel reductions from more efficient land use development patterns.
Land Use Management Strategies
Land use management strategies such as Smart
Growth, New Urbanism and Location-Efficient
Development can reduce per capita automobile use, transportation energy use
and emissions by improving Accessibility and Transportation Options (Donoso,
· 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.
· 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
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.
Ridesharing.
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 (TCRP, 2003). 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 by 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.
High Occupant Vehicle (HOV) Priority
High Occupant Vehicles (HOVs) include carpools, vanpools and transit vehicles. Strategies that give HOVs priority in traffic and parking can result in mode shifting, and smoother traffic flow reduce per-mile energy consumption and pollution emissions. Hossain and Kennedy (2008) estimated that Bus Rapid Transit could reduce corridor transportation energy consumption by 29% in the short-run and 45% over the long run, compared with general purpose lanes. Table 11 summarizes estimated emission reductions from transit priority strategies. HOV facilities can reduce peak-period vehicle trips on a particular roadway by 4-30%, although regional travel reductions are smaller because only congested travel is affected.
Table 11 Bus
Priority Measures in
|
Measure |
Proportion of Buses
Affected |
Exhaust Emission
Reduction Per Bus Affected |
|
Peak period bus lane |
5% |
20% |
|
Contra-flow lane, all day |
2% |
35% |
|
Signal pre-emption |
20% |
12% |
|
Segregated bus street |
2% |
60% |