Modifying urban transportation systems to improve the urban environment

The extensive use of automobiles for transporting people in cities has contributed to a wide variety of urban environmental and economic problems, including poor air quality, excessive energy consumption, traffic congestion, traffic accidents, and disruption of cities as a result of highway construction. These problems can be mitigated through the implementation of measures to discourage the use of low occupancy automobiles and encourage the use of transit and carpools. The most frequently considered measures involve improvements in transit service, carpool locator and incentive programs, and disincentives to low-occupancy automobile use. The latter class of measures includes various approaches to restricting the supply of parking or roadway facilities and increasing the cost of automobile use. Programs that combine all three classes of measures could reduce automobile use in cities by as much as 35% and, thereby, substantially reduce automobile-related urban problems. There is evidence suggesting that reductions in automobile traffic in cities need not disrupt employment and retail activity. However, it will not be possible to reach firm conclusions concerning the effects of traffic reductions on economic activity until there has been more operational experience with traffic reduction programs.