Victoria Transportation Institute

About This Encyclopedia


TDM Encyclopedia

Victoria Transport Policy Institute


Updated 2 April 2014

This chapter describes the Online TDM Encyclopedia and how to use it.


“Our ignorance is not so vast as our failure to use what we know.”

M. King Hubbert, Geophysicist



What is the Online TDM Encyclopedia?

The Online TDM Encyclopedia is the world’s most comprehensive information resource concerning innovative transportation management strategies. It describes dozens of Transportation Demand Management (TDM) strategies and contains information on TDM planning, evaluation and implementation. It has thousands of hyperlinks that provide instant access to more detailed information, including case studies and reference documents.


The Encyclopedia has an international perspective, with ideas and examples from all over the world, including both developed and developing countries. The Encyclopedia is created and maintained by the Victoria Transport Policy Institute (VTPI), an independent research organization located in Victoria, British Columbia.


Vision Statement

The Online TDM Encyclopedia provides information on innovation solutions to transportation problems in an accessible and convenient format. To expand the scope of options and impacts considered in transport planning. To create resources that bridge theory and practice. To facilitate more optimal decision-making. To demonstrate that transportation planning can be interesting and enjoyable.



What is Transportation Demand Management?

Transportation Demand Management or TDM (also called Mobility Management) refers to various strategies that change travel behavior (how, when and where people travel) in order to increase transport system efficiency and achieve specific planning objectives. TDM is increasingly used to address a variety of problems.


A typical person makes more than a dozen trips away from home each week – to work, shopping, errands, social and recreation activities. Many of these trips are flexible in terms of their timing, mode and destination. For example, many commuters can vary when and how they travel to work or school, at least some days. Similarly, errands can be organized in various ways, such as walking or bicycling to neighborhood shops, driving to a downtown or mall, or making several automobile trips to various destinations dispersed along major highways. Recreational activities can also have various travel options, ranging from a neighborhood stroll, driving across town to exercise at a gym, or cycling for errands and commuting. Many factors affect people’s transport decisions including the relative convenience and safety of travel modes (such as whether streets have sidewalks and bikepaths, and the quality of transit services available), prices (transit fares and the price of parking at destinations); and land use factors (such as whether or not schools, parks and shops are located close to residential neighborhoods). Even freight transport often has flexibility in how goods are shipped and deliveries organized.


Transportation Demand Management strategies influence these factors to encourage more efficient travel patterns, such as shifts from peak to off-peak periods, from automobile to alternative modes, and from dispersed to closer destinations.


There are numerous TDM strategies using various approaches to influence travel decisions. Some improve the transport options available; some provide incentives to change travel mode, time or destination; others improve land use accessibility; some involve transport policy reforms and new program that provide a foundation for TDM. Table 1 lists TDM strategies described in this Encyclopedia.


Table 1            TDM Strategies Described In This Encyclopedia

Improves Transport Options


Land Use Management

Policies and


Transit improvements

Nonmotorized improvements

Rideshare programs


Car sharing


Taxi improvements

Bike/transit integration

Guaranteed ride home

HOV Priority

Road pricing

Distance-based fees

Commuter financial incentives

Parking pricing

Pay-as-you-drive vehicle insurance

Fuel tax increases

Nonmotorized encouragement

Smart growth

New urbanism

Location-efficient development

Parking management

Transit oriented development

Car free planning

Traffic calming

TDM Programs

Commute trip reduction

Campus transport management

Freight transport management

Tourist transport management

TDM marketing

Least-Cost planning

Market reforms

Performance Evaluation

This table lists various mobility management strategies



The may be several steps between a particular TDM policy or program, and its desired outcomes, as illustrated below. Although many TDM strategies have modest impacts, only affecting a few percent of total trips, their impacts are cumulative and synergistic (total impacts are larger than the sum of individual impacts). A comprehensive TDM program can often affect a significant portion of total travel and provide large total benefits. It is therefore important to plan and evaluate integrated TDM programs rather than individual strategies.


Steps In TDM Implementation

Policy and Planning Reforms

(more funding for alternative modes, increased support for TDM programs, changes in land use planning practices, etc.)

Changes Travel Options and Incentives

(improved walking and cycling conditions, improved ridesharing and public transit services, more compact and mixed land use development, increased road and parking fees, reduced transit fares, etc.)

Travel Changes

(shifts in travel time, route, mode, destination and frequency)


(reduced traffic congestion, road and parking facility cost savings, accident reductions, energy conservation, pollution emission reductions, improved mobility for non-drivers, etc.)




Why Manage Transportation Demand?

This section describes various reasons to implement TDM solutions. For more information see Why Manage Transportation Demand?



Multiple Benefits

By reducing total vehicle traffic and improving overall Accessibility, Transportation Demand Management provides multiple benefits, including those described in Table 2. Although not every TDM strategy achieves all of these benefits in every situation, most strategies help achieve most of these benefits in most situations.


Table 2          Typical TDM Benefit



Congestion Reduction

Reduces traffic congestion delays and associated costs.

Road & Parking Savings

Reduces road and parking facility costs.

Consumer Savings

Helps consumers save money by reducing their need to own and operate motor vehicles.

Transport Choice

Improved travel options, particularly for non-drivers.

Road Safety

Reduced crash risk

Environmental Protection

Reduced air, noise and water pollution, wildlife crashes and other types of environmental damages.

Efficient Land Use

Supports strategic land use planning objectives, such as reduced sprawl, urban redevelopment and reduced habitat fragmentation.

Community Livability

Improved local environmental quality and community cohesion.

Economic development

Supports a community’s economic objectives, such as increased productivity, employment, wealth, property values and tax revenues.

Physical Fitness and Health

Improved public fitness and health due to more physical activity, usually through increased daily walking and cycling.

Most TDM strategies help achieve most of these benefits in most situations. Conventional transport planning that focuses on just a few impacts tends to undervalue TDM.



Most conventional transport improvement strategies only solve one or two problems, but due to Rebound effects (they stimulate additional vehicle travel) they exacerbate others. For example, widening roadways may reduce traffic congestion (at least for a while) but by generating additional vehicle travel it tends to increase problems such as downstream traffic and parking congestion, energy consumption and sprawl. Similarly, more efficient and alternative fuel vehicles may reduce energy problems and pollution emissions, but by reducing the per-mile cost of driving they tend to increase problems such as traffic and parking congestion, accidents and sprawl.


Conventional transport planning practices tend to focus on a limited set of impacts and so tend to undervalue TDM. For example, conventional planning often focuses on motor vehicle congestion, vehicle operating costs and accident rates, but ignores delays to pedestrians and cyclists, vehicle ownership costs, and physical fitness and public health impacts. Many of the methods used to measure transport system quality are biased in favor of automobile travel. For example, conventional planning often uses a congestion index (the ratio of actual vehicle traffic speeds to uncongested travel speeds) and motor vehicle crash rates per 100 million vehicle-miles to identify problem areas; indicators that focus on automobile travel conditions and ignore the costs of increased vehicle travel. For example, if vehicle travel increases 30% but traffic congestion delays and fatalities only increase 20%, the congestion index and crash rate values will decline, implying that travel has become easier and safer, although total delays and deaths actually increase. Conversely, they would consider harmful a TDM strategy that reduces vehicle travel by 30% if it only reduces congestion and accident costs by 20%. Transport planning must apply more Comprehensive Evaluation to determine the full benefits of TDM.


Cost Effective

When all impacts (benefits and costs) are considered, Transportation Demand Management strategies are often the most cost effective way to improve transportation. TDM can defer and reduce the need to expand roads and parking facilities, and provide other benefits such as reduced traffic accidents, energy conservation, and improved mobility for non-drivers.



TDM can provide flexible responses to many types of transportation problems, including those that are urgent, temporary, variable or unpredictable. TDM programs can be implemented quickly, and tailored to a particular situation and user group. Demand management avoids the risk that a major capital investment will prove wasteful due to unforeseen changes in transportation needs.


Consumer Benefits

TDM can provide various consumers benefits. Many TDM strategies use positive incentives, they improve transportation options and provide financial rewards, and consumers benefit from reduced traffic congestion, parking problems, crash risk and pollution emissions.



TDM can help achieve Equity objectives. It can result in a fairer allocation of resources between different demographic and geographic groups. Many strategies directly benefit people who are economically, physically or socially disadvantaged by improving transportation options available to non-drivers.


Economic Justifications

Many Transportation Demand Management strategies reflect Market Principles. They correct existing market distortions, which increases economic efficiency, equity and consumer benefits. TDM supports economic development by increasing productivity and reducing external costs.


Sustainable Transportation

Transportation Demand Management can help create more Sustainable Transportation. TDM reflects sustainability principles of efficiency and integration, and can help achieve sustainability objectives including resource conservation, equity, environmental protection, efficient land use, and public involvement.



TDM Strategies

This Encyclopedia includes chapters on specific TDM strategies. Each strategy is described, categorized and evaluated as listed below.



This includes a general description of each strategy.


How It Is Implemented

This section describes how a strategy is typically implemented.


Travel Impacts

This describes how a strategy affects vehicle travel. A table such as the one below summarizes these travel impacts. Ratings range from 3 (very beneficial) to –3 (very harmful). A 0 indicates no impact or mixed impacts. Additional technical information on factors that influence travel demand is provided in chapters on Transportation Elasticities, Land Use Impacts on Transportation and Evaluating Nonmotorized Transport.


Travel Impact Summary

Travel Impact



Reduces total traffic.


Indicates whether a strategy reduces overall vehicle travel.

Reduces peak period traffic.


Indicates whether a strategy reduces vehicle travel during peak periods.

Shifts peak to off-peak periods.


Indicates whether a strategy encourages motorists to shift from peak- to off-peak driving.

Shifts automobile travel to alternative modes.


Indicates whether a strategy encourages shifts to alternative modes in general.

Improves access, reduces the need for travel.


Indicates whether a strategy improves land use access, and therefore reduces the need to travel.

Increased ridesharing.


Indicates whether a strategy encourages ridesharing.

Increased public transit.


Indicates whether a strategy encourages public transit use.

Increased cycling.


Indicates whether a strategy encourages cycling.

Increased walking.


Indicates whether a strategy encourages walking.

Increased Telework.


Indicates whether a strategy encourages use of telecommunications to substitute for physical travel.

Reduced freight traffic.


Indicates whether a strategy reduces freight travel.

Ratings range from 1 (minimal impact) to 3 (significantly contributes to this impact).



Benefits and Costs

This section discusses the benefits and costs of each strategy (Evaluating TDM). A table such as the one below summarizes each strategy’s effectiveness at achieving various transportation improvement objectives. For example, a strategy that shifts vehicle traffic from peak to off-peak time periods could have a high congestion reduction rating but a low environmental protection rating, while a strategy that mainly reduces rural or off-peak vehicle travel may have a low congestion reduction rating but a higher environmental protection rating.


Benefit Summary




Congestion Reduction


Indicates whether a strategy reduces traffic congestion.

Road & Parking Savings


Indicates whether a strategy reduces roadway and parking facility costs by reducing automobile travel and trips.

Consumer Savings


Indicates whether a strategy provides consumer savings by reducing vehicle costs, improving the availability of affordable travel modes, or by providing direct financial benefits to consumers.

Transport Choice


Indicates whether a strategy increases consumers’ transport choices, particularly for non-drivers.

Road Safety


Indicates whether a strategy reduces the risk of traffic crashes, and associated damages and injuries.

Environmental Protection


Indicates whether a strategy reduces air, noise and water pollution, resource consumption, impervious surface, habitat loss and other environmental impacts.

Efficient Land Use


Indicates whether a strategy encourages clustered, infill, multi-modal development, as opposed to dispersed, urban periphery, automobile-dependent development.

Community Livability


Indicates whether a strategy helps create more aesthetically attractive and pedestrian-friendly streetscapes, neighborhood interaction, and preservation of unique cultural features.

Ratings range from 3 (very beneficial) to –3 (very harmful). A 0 indicates no impact or mixed impacts.



Equity Impacts

This discusses a strategy’s equity impacts as described in Evaluating TDM Equity. A summary table such as the one below is used to evaluate a TDM strategy’s impacts according to five equity criteria.


Equity Summary




Treats everybody equally.


Indicates whether a strategy treats each group or individual equally.

Individuals bear the costs they impose.


Indicates whether a strategy helps make the prices of transportation services more accurately reflect the costs of that service, reducing cross-subsidies.

Progressive with respect to income.


Indicates whether a strategy increases Transportation Affordability and makes lower-income households better off.

Benefits transportation disadvantaged.


Indicates whether a strategy makes people who are transportation disadvantaged better off.

Improves basic mobility.


Indicates whether a strategy helps provide basic mobility.

Ratings range from 3 (very beneficial) to –3 (very harmful). A 0 indicates no impact or mixed impacts.




This section describes the situations in which a strategy is most suitable. A table such as the following is used to indicate how appropriate a strategy is for implementation in various geographic and organizational conditions. Ratings range from 0 (not appropriate) to 3 (very appropriate).


Application Summary





Large urban region.


Federal government.


High-density, urban.


State/provincial government.


Medium-density, urban/suburban.


Regional government.




Municipal/local government.


Low-density, rural.


Business Associations/TMA.


Commercial center.


Individual business.


Residential neighborhood.




Resort/recreation area.


Neighborhood association.






Ratings range from 0 (not appropriate) to 3 (very appropriate).




TDM strategies are assigned to one or more of these categories:


·         Policy And Institutional Reforms. These are organizational changes that overcome barriers and provide support for TDM implementation.


·         TDM Programs and Program Support. A program implements a suitable combination of complementary TDM strategies. Programs have specific goals and objectives, responsibilities and activities, staff and budgets.


·         Improved Transport Choice. These strategies improve the range and quality of transportation services available to target populations.


·         Incentives To Use Alternative Modes and Reduce Driving. These strategies include various incentives that encourage people to shift to more efficient transportation options.


·         Land Use Management. These strategies result in more accessible land use patterns that reduce the need for travel and make alternative modes more convenient.



Relationships With Other TDM Strategies

This section describes other TDM strategies it supports and is supported by. These are linked within the Encyclopedia, so you can go directly to that chapter.



This section describes which groups or organizations typically support or oppose a strategy.


Barriers To Implementation

This section describes major barriers to implementation of the strategy, and ways to overcome these barriers.


Best Practices

This section describes the best way to implement the strategy.


Examples and Case Studies

This section provides examples and case studies illustrating implementation of the strategy.


References And Resources For More Information

This section provides information on publications and organizations related to this strategy, many accessible through the Internet.



Choosing TDM Strategies

The information in this Encyclopedia can help you identify the combination of strategies that are most appropriate for a particular situation. For example, the ratings provided for each TDM strategy can help identify strategies that a suburban city government can use to reduce traffic congestion, or that neighborhood groups in a resort area can use to increase community livability and environmental protection. Of course, these ratings represent general trends and may not apply in all situations, so users should use their own judgment when evaluating strategies.


In most situations it is best to develop a TDM program that includes a combination of complementary strategies. For example, a suburban city government that wants to reduce congestion might develop a program that includes Ridesharing, Commute Trip Reduction, School Transport Management, Shuttle Services and Parking Pricing. Together these strategies can be more effective and cost effective than if they are implemented alone. The “Relationships With Other TDM Strategies” section in each TDM strategy chapter can help identify which strategies are best implemented together.


Other chapters related to planning, evaluation and reference information can provide further help selecting the best combination of strategies and developing the most effective TDM program to implement in a particular situation.



Other Chapters

The Encyclopedia includes chapters on various issues related to TDM planning and evaluation. Some of these are described below.



These chapters describe this Encyclopedia and TDM.


Why Manage Transportation?

This chapter discusses reasons to consider TDM solutions to transportation problems.


Success Stories

This chapter describes examples of successful TDM programs.


Win-Win Transportation Solutions

This chapter describes several TDM strategies that provide a combination of economic, social and environmental benefits. These Win-Win Solutions help achieve sustainable transportation.



Strategies To Achieve Specific Objectives

These chapters describe and rank strategies for achieving specific objectives.


Congestion Reduction Strategies

Describes strategies for reducing traffic congestion.


Energy Conservation and Emission Reduction Strategies

Describes strategies for reducing vehicle energy consumption and pollution emissions.


Health and Fitness

Strategies that improve public health and fitness through physical activity.


Improving Equity

Strategies that are particularly helpful for achieving equity objectives.


Livability Strategies

Describes strategies to help make a community a desirable place to live, work and visit.


Parking Solutions

Solutions to parking problems.


Safety Strategies

Describes strategies for improving traffic safety and public health.



TDM Planning and Evaluation

These chapters provide information on TDM planning and evaluation techniques.



Describes the concept of accessibility, how it is evaluated, and ways to improve access.


Automobile Dependency

Transportation and land use patterns that cause high levels of automobile use and reduced transport options.


Basic Access

This chapter describes the concepts of “Basic Access” and “Basic Mobility,” which refer to transport activities that society values highly. It discusses how these concepts can be applied in transport planning.


Comprehensive Transportation Planning

Describes how to create a comprehensive framework for planning and evaluating transportation.


Evaluating Criticism of TDM

Evaluates various criticisms of TDM, including claims that demand management is harmful to consumers and the economy, unfair and ineffective.


Land Use Evaluation

This chapter examines how transportation decisions affect land use patterns, and the economic, social and environmental impacts that result.


Evaluating Nonmotorized Transport

Describes techniques for measuring nonmotorized travel demand, evaluating nonmotorized conditions, and incorporating nonmotorized travel into transport models.


Evaluating Pricing Strategies

Discusses factors to consider when evaluating TDM strategies that involve price changes.


Evaluating TDM

Describes methods for evaluating TDM, and how this Encyclopedia can help evaluate TDM programs.


Equity Evaluation
Discusses concepts of transportation equity, and criteria used in this Encyclopedia to evaluate the equity impacts of individual TDM strategies.


Evaluating Transportation Options

This chapter describes the benefits of having a diverse, balanced transportation system and several methods for evaluating these benefits.


Market Principles

Discusses the general principles of an efficient and equitable market, how well these principles are reflected in current transportation and land use markets, and the degree to which TDM strategies support these principles.


Health and Fitness

Discusses how TDM can help increase physical activity, health and fitness.


Performance Evaluation

This chapter discusses specific ways to evaluate the effectiveness of TDM programs.


Evaluating Resilience and Security

Explores the concepts of resilience and security and their implications for transportation planning.


Measuring Transportation

Discusses various ways to measure transportation performance and their implications for transportation planning.


Pricing Methods

Describes and compares methods of collecting road tolls, parking fees and mileage charges.


Rebound Effects

Discusses “Rebound Effects” and their implications for transportation planning.


Evaluating Safety Impacts

Discusses how TDM strategies impact traffic safety, personal security and health.


Transit Evaluation

Provides comprehensive information on methods and data sources for evaluating public transit service.


Sustainable Transport and TDM

Discusses how TDM can help achieve more sustainable transport, and how incorporating sustainability goals in planning can support TDM.


TDM and Economic Development

Examines how TDM affects economic productivity and development.


TDM Planning

Discusses various issues to consider when planning and implementing Transportation Demand Management programs.



Reference Information

These chapters provide additional technical information about TDM.


Costs of Driving

Describes the costs of driving and the savings that result from reduced vehicle use.



Defines special words used for TDM planning.


Land Use Impacts on Transport

Describes how land use patterns affect travel behavior.


Prestige and Pleasure

Discusses mobility as a prestige good and as a pleasurable activity – implications for transport planning.


Potential TDM Strategies

This paper briefly describes the various types of TDM strategies.



Publications and websites for more information on TDM.


Transportation Statistics

Describes sources of information about transportation activities throughout the world.


Transportation Costs & Benefits

Information on various transportation costs and benefits.


Transportation Elasticities

Describes how user costs (fuel prices, parking charges, vehicle fees, fares, etc.) affect travel behavior.


Trip Reduction Tables

Describes how parking prices and commuter benefits affect commute travel patterns.


Wit and Humor

To add a little fun, jokes and clever quotes are scattered through the Encyclopedia. This chapter has all of them, at least the introduction to each one. Follow the links to the punchlines.



References and Information Resources

Each Encyclopedia chapter has a References and Information Resources section which provides more detailed information on each subject. Over the years we have used various bibliographic formats. Based on this experience we have developed a format which we think is useful, readable and flexible.


We consider each bibliographic entry to be a sentence, and so use commas as separators and a period at the end. We use first and last names, followed by publish year in parenthesis. We bold the first author’s last name to make it easier to find, and to clarify distinctions between personal and corporate names (Suzanne Kort versus Suzanne Kort Inc.). We include a publisher website in parenthesis (if available, we don’t bother with publisher’s city), and if possible we include a specific URL for the document (these often change of time, so it is often necessary for users to search the publisher’s website). We sometimes include a description of the document.


Standard formats:


Author first and last names (publish year), “Article Title,” Title, publisher, vol. and no. (publisher website or city); specific website URL. Any descriptive information or additional comments.


Internet Resource (URL), sponsoring organization and any descriptive information.

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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