WORK
BY DEBORAH L. JOHNSON
WORK
BY DEBORAH L. JOHNSON
Transportation demand management (TDM) is a term used for a set of mechanisms intended to influence individual travel behavior. Such measures include both incentives ("carrots") that promote desirable behavior and disincentives ("sticks") that frustrate undesirable behavior. Much has been written about specific TDM strategies1 that conceptualizes how they might operate and debates their viability and efficacy. However, examples that suggest how TDM theory might be bridged with the political realities of practice are limited. This paper explores legislative options for implementing TDM measures at the state level. Statutes from selected states are evaluated to determine the potential for adapting existing legislation as a model, culminating in three suggested legislative approaches and a proposal for elements that should be addressed as additional states consider legislation.
Demand management offers a tool for addressing several issues. A principal, while perhaps obvious, goal of TDM is to relieve traffic congestion by reducing the number of auto trips taken, vehicle trips during peak travel times, and the drive-alone rate (Schauer 1994). Another commonly cited goal is diminishing air pollution; a third is reducing fossil fuel consumption.2 Hanson (1992) suggests that TDM may also affect highway safety, including accident-related injuries, fatalities, property damage to vehicles, transportation infrastructure, and other property;3 the opportunity cost incurred when land that could have been used for some other purpose is used for car-related infrastructure; and environmental degradation resulting from surface water runoff from roadways which, in addition to road salt in some areas, may contain petroleum products and other contaminants.
In economic terms, TDM is a demand-side strategy as opposed to the traditional supply-side strategy of increasing the transportation system's carrying capacity by building more roads (Downs 1992). Demand management measures are derived from the 1970s concept of transportation system management (TSM), which includes supply-oriented strategies as well (Giuliano 1992).4 Downs portends that supply-side strategies alone, such as adding more roads, widening existing roads, installing transit, and even technological solutions (i.e., "intelligent vehicle highway systems"), are insufficient to diffuse congestion (Lincoln Institute of Land Policy 1993). The increasing use of TDM measures indicates a paradigm shift from the historic public-sector stance of providing infrastructure and perpetuating automobile reliance in other ways, instead focusing on understanding and responding to the movements of people rather than cars (Schauer 1994).
In order for legislators to form reasonable expectations about the use of TDM measures, several structural and political circumstances must first be recognized. These are offered as assumptions upon which adoption of TDM legislation is predicated: if legislation is adopted without an appreciation of these conditions, it is more likely to be flawed and publicly unpopular. This does not suggest that it will be perfect and readily accepted otherwise, but rather that elected officials and public administrators will be better prepared to formulate workable standards.
Cooper (1971) defines transportation planning as a continuous process of developing an advance course of action for achieving transportation goals by offering an adequate quantity and quality of transportation modes, coordinating balance between these modes, and incorporating flexibility to enable innovation. In order to be effective, he maintains that it must be carried out in the context of comprehensive planning; likewise, planning for individual modes must be a part of overall transportation planning. Central to the planning function is the belief that it is possible to find holistic solutions to social problems that are better than individual approaches (Bly in Nijkamp and Reichman 1987).
Perhaps most important to TDM's effectiveness is a regional approach that cooperatively involves agencies, governments, and various interest groups (Schauer 1994). The Institute of Transportation Engineers suggests that the most useful combination of TDM strategies is best identified at the state and local levels in consideration of differing regional needs and constraints (Nadis and MacKenzie 1993). This comprehensive, regional approach is linked to the physical attributes of development that must occur in order to relax reliance on the automobile.5 Examples of how this draws in zoning and land-use practices include deintensification into mixed-use centers that put everyday retailers and services (and even jobs) within walking distance and the use of pedestrian-oriented, transit-supportive design. Design is important in attaining accessibility, says Handy (1993), and we must come away from our current automobile orientation in order to decrease congestion and increase access. This shapes a central assumption in promulgating legislative approaches to TDM: that such measures are necessarily being considered in the broader context of comprehensive planning and are intended to operate in concert with the supply-side (system management) strategies that comprehensive planning includes.
Demand management is not without its detractors. As early as the 1910s, the Los Angeles media, business community, Motor Car Dealers Association, and motorists successfully coalesced against unwanted parking restrictions in the downtown area (Bottles 1987). When combined with popular preference for the automobile, the U.S. tradition of freedom and democracy render TDM mechanisms less acceptable here than in nations whose political atmosphere is more restrictive. Because our society embraces individual choice and free-market economics, it is unrealistic to expect people to stop using their cars until forced to do so (Bottles 1987).
Reshaping drivers' attitudes is difficult, concludes Flannelly and McLeod (1989) because cars are publically perceived to be a "least-cost" travel option in terms of the amount of time and effort drivers must expend to arrange alternatives. From this perspective, it seems unlikely that favorable attitudes toward individual driving can be readily changed because they are deeply seated in the quality of service the car offers as opposed to other transportation modes. Even if people believe that worthwhile societal goals or personal economic gains are served by shifting their mode of travel, they may decide that using alternate modes is not worthwhile given their costs in terms of inconvenience. Therefore, approaches that are most likely to be publicly accepted are those that expand individual freedoms by broadening travel options rather than those that constrict them (Webber 1973).6
Ferguson (1990) is one of few researchers who explore the role of the development community in implementing TDM. Yet he cautions that developers are concerned about potential restrictions TDM measures will place on their exercise of private property rights. This issue has recently moved to the forefront of political discussion at both the national and state level as legislation is introduced that significantly redefines regulatory takings to include actions that restrict - often in even minor ways - the economic value of land. The relationship between such legislation, if enacted, and TDM remains to be seen.
That elected officials and public administrators fully acknowledge such conflicts is another essential assumption. Economists' dreams of such mechanisms as congestion pricing can be politicians' nightmares (Small 1993). Without this recognition and a clear commitment to using TDM in the face of controversy, uncertain leadership could lead to a breakdown of any TDM process that is proposed.
Can TDM successfully resolve all of the problems it is intended to address? Most researchers seem dubious, especially given public attachment to the automobile. Even more enthusiastic proponents like Nadis and MacKenzie (1993) point out that no single measure can solve all transportation problems and conclude that the best that can be sought is a combination of steps to ease the related problems of air pollution, congestion, and urban sprawl. Perhaps Ferguson (1990) puts it most clearly: the only obvious message about TDM implementation "is that it is a very 'messy' business, requiring cooperation and support from many different groups within the community in order to achieve any measurable success."
Our ability to measure that success is another matter. Ferguson calls for additional research toward evaluating TDM programs, especially given the difficulties of individually measuring the effects of separate TDM measures that are comprehensively employed. Because many TDM efforts are targeted at work trips, it is important to consider that the nature of work trips has changed as traffic patterns have followed population shifts resulting from land-use policies (again promoting the need for comprehensive policy making).
With 86 percent of population growth since 1950 and two-thirds of new jobs from 1960 to 1980 occurring in suburban areas, suburb-to-suburb drives now account for less than 20 percent of all trips (Deakin 1991) and the traditional suburb-to-city commute represents only about ten percent of all works trips (Nadis and MacKenzie 1993). This shifting system in which TDM operates frustrates attempts to measure its efficacy. A final assumption, therefore, is that TDM is not a panacea but rather a tool that must be responsive to a dynamic structure.
1. An array of such measures is included in the sidebar "Compilation of Transport Demand Management Measures" in this paper. Discussions on advantages and drawbacks of various approaches may be found in source documents.
2. The last goal is more prevalent in 1970's literature, which tended to focus on concerns about oil depletion and the energy crisis of the time period.
3. Also implicit in considering highway safety is the level of emergency response (policing, medical services, fire suppression, and incident response) that is required to be available.
4. Ferguson (1990) suggests a more complementary role for TDM and TSM in in balancing their demand-oriented and supply-oriented strategies, rather than the first being a subset of the second. Moore and Thorsnes (1994) expand on Ferguson's position, adding that the distinction between the two blurs because supply-side policies often affect demand.
5. Freilich and White (1991); Moore and Thorsnes (1994); and Wickersham (1994) all cogently discuss the relationship between land use and transportation.
6. Giuliano (1992) corroborates this finding in noting that necessary qualities of TDM incentives are not sufficient if measures do not find public acceptance. Those noted to have met with the strongest public acceptance. Those noted to have met with the strongest public opposition imposed controls and reduced the range of choices. Public acceptance is more likely when incentives offer commuters a wide range of choices and flexibility, she concludes.