CAN MANAGEMENT OF TRANSPORTATION DEMAND HELP SOLVE OUR GROWING TRAFFIC CONGESTION AND AIR POLLUTION PROBLEMS

Abstract

Once considered a speculative concept, transportation demand management (TDM) is entering the mainstream of professional thinking and acquiring political legitimacy. Support for TDM is particularly strong in jurisdictions in which budgetary constraints, environmental concerns or community opposition render the prospect of major new highway construction highly problematical. However, enthusiasm for TDM is by no means universal. Besides philosophic objections that demand management represents an unwarranted government intrusion into personal lives, genuine doubts persist about the ability of demand management to significanty reduce automobile usage. Assessment of TDM, based on an evaluation of numerous TDM programs around the country, indicates that, while TDM is not the magic solution that some of the more uncritical advocates would have us believe, it is a useful addition to our arsenal of traffic mitigation tools. Just how important a role demand management will play in the battle against traffic congestion and air pollution is uncertain at this time. The following conclusions can be drawn at this stage of TDM evolution: (1) Little effort has been devoted to evaluating the effectiveness of demand management in a balanced and dispassionate way; (2) Uniform comparisons are rendered difficult because there is no agreement on how to assess TDM effectiveness; (3) Although some successes are evident, there is no evidence that they can be replicated widely enough to influence traffic congestion or air quality on a regional or sub-regional level; (4) There is a tendency to ignore the principle of latent demand; (5) Effective travel demand management is not cost-free; (6) Congestion pricing, despite its theoretical appeal, faces many hurdles; and (7) Well-meaning but overzealous attempts to oversell the promise of demand management may give local officials a false sense of confidence and cause them to set unrealistic goals for traffic reduction.