The influence of U.S. transportation on several critical natural resources and environmental systems is reviewed in this report along with several policy and technology options for lessening this influence. The purpose of the review is to identify some of the challenges that lie ahead in managing transportation's long-term environment effects and the kinds of research and preparations that are needed to inform policy and meet these challenges. Although the report does not recommend specific policies to pursue, it identifies some of the issues and uncertainties that will need to be addressed in evaluating them. The discussion focuses on motor vehicle transportation, which accounts for most of the energy consumed, pollutants emitted, and physical infrastructure used by the U.S. transportation system. Whether motor vehicles will continue to exert such dominance over the next several decades cannot be anticipated. Nevertheless, should moor vehicle travel grow at even half the rate experienced during the post half-century, the amount of travel by motor vehicles on the nation's roadways will more than double before the middle of the next century. An escalation in motor vehicle travel of this magnitude, or even on amore modest scale, will have important implications for environmental policy. Whereas the focus of this report is on the large motor vehicle tranportation system, similar assessments of other fast-growing transportation modes, such as air travel, may be warranted. (A)
Samenvatting