A number of state governments have recently passed legislation aiming to rein in vehicle miles traveled (VMT), and many cities have begun to take action to reduce VMT in their jurisdictions. Policymakers often want to know what they should do to encourage less driving. Unfortunately, there is no “one size fits all” solution. The effectiveness of various policy options depends critically on context: who is driving, where are they going, and what alternative modes and destinations are available.

Fortunately, there is an extensive body of academic literature on this topic that practitioners can tap into when considering various policy options. This policy brief summarizes findings from the white paper examining this literature.

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This dissertation is an exploration of the relationship between the transportation-land use system in New York City and the transportation and residential location choices made by New Yorkers. The focus is on understanding these location and travel choices made by urbanites. Specifically, this research uses discrete choice models to identify and quantify the effects of the variables that factor into New Yorkers' decisions about where to live, whether to own a car, and how to get around in their daily lives. These models, along with GIS technology, are used to answer the following questions:

1. How far off are the results of models that do not take all three of these decisions as endogenous?

2. In a densely populated urban environment, what are the policy-sensitive factors that determine whether households own cars and how often walking is the mode of choice?

3. How does the relative importance of these factors change across different neighborhoods within the city?

4. How much of the relationship between land use patterns and travel behavior is due to the indirect effects of neighborhood and car ownership choice, and how large is the direct effect of land use patterns on travel behavior?

Results indicate that the choices of residential location and commute mode are closely related; models of only commute mode choice produce biased results. Models that do not take the choice of car ownership as endogenous in New York do not appear to be severely biased.

Full models of the three choices indicate that the most important policy- sensitive factors influencing car ownership and mode choice are commute cost, commute time, and population density. A set of spatial scenario analyses illustrate that the importance of these factors does indeed vary across neighborhoods within the city.

Finally, a methodology is developed to separate the direct effect of land use patterns on travel behavior from the indirect effects. The example used here identifies the direct and indirect effects of population density on the propensity to walk, finding that approximately half of the total effect is direct.

Cities around the world are trying out a multitude of transportation policy and investment alternatives with the aim of reducing car-induced externalities. However, without a solid understanding of how people make their transportation and residential location choices, it is hard to tell which of these policies and investments are really doing the job and which are wasting precious city resources. The focus of this paper is the determinants of car ownership and car use for commuting. Using survey data from 1997 to 1998 collected in New York City, this paper uses discrete choice econometrics to estimate a model of the choices of car ownership and commute mode while also modeling the related choice of residential location.

The main story told by this analysis is that New Yorkers are more sensitive to changes in travel time than they are to changes in travel cost. The model predicts that the most effective ways to reduce both auto ownership and car commuting involve changing the relative travel times for cars and transit, making transit trips faster by increasing both the frequency and the speed of service and making auto trips slower – perhaps simply by allowing traffic congestion. Population density also appears to have a substantial effect on car ownership in New York.

Policymakers aiming to reduce vehicle miles traveled (VMT) want to know what they should do to reduce the amount people drive, and what evidence suggests that this is the best course of action. The relationships between built environment characteristics and driving have generally been shown to be consistent with expectations. As alternatives to solo driving become available, people drive less. As driving becomes more expensive and less convenient, people drive less. As trip destinations and origins move closer together, people drive less. Based on this evidence, policymakers should not hesitate to enact policies and make prudent investments that encourage less driving. However, despite an extensive academic literature on this subject, the specific answer to the policymaker’s question is not straightforward. There is a wide variety of possible policy actions, and the action(s) that will be most effective in a particular situation depend critically on context: who is driving, where they are going, and what alternative modes and destinations are available. Existing research results can provide guidance but cannot dictate a universally applicable recipe. This white paper provides a guide for practitioners on how to read, understand, and use results reported in this especially challenging area of the literature: the relationship between the built environment, the transportation system, and driving. It identifies theoretical relationships, highlights the challenges inherent in exploring these relationships using real-world data, and discusses three prominent studies in detail to illustrate how to interpret the results.

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Worldwide, greenhouse gas emissions are rising faster in transportation than in any other sector. Rapid motorization — more cars and trucks — is the principal cause. This report focuses on the challenges faced by developing countries in accommodating and managing motorization and the demand for improved transportation.

Enhanced mobility has many positive effects on economic development and social welfare, including more efficient movement of goods and improved access to jobs, health services, and education. However, if enhanced mobility is achieved primarily through increased reliance on conventional private cars, it can mean diverting substantial financial resources to roads and suffering worse air pollution and traffic congestion. The benefits are enormous, but the costs can also be substantial. These positives and negatives are accentuated in the developing nations of Africa, Asia, and Latin America. Most are experiencing rapid population growth and urbanization, and many have fast-growing economies. The number of private vehicles is increasing in almost all developing countries.

The challenges posed by motorization are unprecedented for these countries. When the more developed countries were building their transportation infrastructure, their populations were small compared to those in much of today’s developing world, and the cost of motorized vehicles was relatively high. Today’s megacities of the developing world are already huge and still expanding. There is little time or money to build public transportation systems or to expand roads to handle the new traffic. They are already experiencing serious congestion, economic and environmental damage, and major safety problems. Yet the problems are not uniform; each city and country faces different circumstances.

This report provides a broad characterization of transportation in developing countries, identifying common challenges and opportunities for policymakers, and suggesting policy options that aim to slow the growth of greenhouse gas emissions from the transportation sector.

The most important observations of this report are the following:

• Rapid motorization — and rapid growth in transportation-related greenhouse gas emissions — are unavoidable in most developing nations. Most developing countries today have low per capita transportation emissions, largely because few people have access to personal transportation. Rapid motorization is transforming transportation and accelerating increases in greenhouse gas emissions.

• The relationship between car ownership and income is not fixed. While it is true that income is the primary force of motorization — explaining perhaps half the growth in vehicle ownership — there is much variation in vehicle ownership among cities and countries at similar income levels.

• Once people have personal vehicles, they use them even if alternative transportation modes are available. This is because the variable cost of operating a vehicle is relatively low compared to the fixed cost of purchasing one.

• There are many sensible policies and strategies that would slow the growth of transportation sector greenhouse gas emissions. Key strategies include increasing the relative cost of using conventional private cars and enhancing the quality and choices of alternative transportation modes.

• Many of the strategies for slowing and eventually reducing greenhouse gas emissions from transportation have local as well as global benefits. Local benefits include reduced air pollution, less traffic congestion, and lower expenditures for road infrastructure.

This report explores strategic paths and alternative futures that could break the link between economic and greenhouse gas emission growth in developing countries. Successful efforts underway in some developing countries — examples of which are highlighted in some of the case study reports that contributed to this overview — demonstrate that developing countries can forge a more sustainable transportation future. Is there a single city that can be looked to as a model for others? This report suggests that the answer is “no.” There are cities and countries that have embraced innovative and effective strategies, but none represents a universally applicable model or pathway.

Energy use and carbon emissions around the globe are increasing faster in transportation than in any other sector, and transportation emissions are increasing fastest of all in developing countries. This report does not suggest that developing nations should adopt entirely different transportation systems than currently operate in more developed countries. There is no perfect solution or leapfrog technology at hand. The reality is that most transportation modes and technologies are already being used internationally. The fundamental desire for personal transportation, and for greater mobility at lower cost, is universal. It is neither realistic nor fair to ask those in the developing world to deprive themselves of the things they need and want, from meeting their basic transportation needs to having access to cars.

Instead, this report suggests that developing countries can choose a more sustainable growth path. They can learn from the experiences of industrialized countries in crafting integrated land use and transportation plans, encouraging more efficient forms of vehicle ownership and use, and accelerating the introduction of environmentally sensible vehicle technologies and fuels. Indeed, as a 1996 U.S. National Academy of Sciences report concluded, “greater reliance on nonpolluting modes of transportation in developing-country cities, coupled with the strong integration of residential and economic activities, suggests those cities may be in a position to avoid some of the most costly mistakes of transportation investment in the industrialized countries.”1

However, the economies and populations of many of these cities are growing at unprecedented rates and personal vehicles are often available to people with very low incomes. Policy and investment decisions with far-reaching implications must be made quickly, or the consequences could be catastrophic — economically, environmentally, and socially. But even with the greatest sophistication and best managers, the choices are not obvious. Simply replicating the choices of other cities in most cases would be ineffective. The elements of a successful transportation strategy are likely to vary greatly depending on local circumstances and institutional strengths and weaknesses.

Without new measures, greenhouse gas emissions from transportation in the developing world will exceed those in the industrialized world sometime after 2010. While the need to limit greenhouse gas emissions may not be a driving force for developing countries in the foreseeable future, many of the strategies that could reduce greenhouse gas emissions would also address the more immediate problems of local air pollution, access to basic transportation, and infrastructure financing pressures. This report focuses on strategies and policies that not only slow the growth of greenhouse gas emissions, but also help achieve local priorities.

In November 1998, the California Air Resources Board modified its Zero Emission Vehicle (ZEV) "mandate" so as to allow certain vehicles with measurable tailpipe emissions to earn partial credit toward the 10% requirement scheduled for 2003 and beyond. This change in the ZEV mandate provides automakers with a greater incentive to market a broad range of very low-emitting vehicles, and reduces the requirement for ‘pure’ zero-emission vehicles. Partial ZEV credits will be given to vehicles that have very low tailpipe emissions, all-electric driving capability, integrated advanced componentry; and use inherently clean fuels. Even very clean-burning gasoline vehicles can earn partial ZEV credit. This report describes the methods and conditions for granting partial ZEV credits, examines credit allocations to particular technology and fuel options, and explores the implications of the proposed changes.

Land development and vehicle travel continue to outpace population growth. Efforts to manage this growth and the adverse impacts associated with it have been mostly ineffective. Promising technology solutions include telecommunications (telecommuting, electronic commerce, teleconferencing, etc.), small personal vehicles (electric bikes and neighborhood vehicles); and new "smart" transport modes (car sharing, "smart" paratransit, etc.).

These options have the potential to be environmentally and economically superior to today’s car-dominated system. Yet none have flourished. Why? One hypothesis is that many automobile substitutes and complements have been rejected because they have been introduced individually and incrementally - not as part of a coordinated transportation system

New mobility is a fundamentally new approach to this problem, focusing on intermodal clustering of innovative technologies with existing transportation options to create a coordinated transportation system that could substitute for the traditional auto. The concept of new mobility was explored at a workshop hosted by the Institute of Transportation Studies at the University of California, Davis on November 2, 1998. This report describes the technologies of new mobility and suggests ways that they might be coupled together through public-private partnerships and experimentation at the local level.