The continuous rapid growth in vehicle miles travelled coupled with the rapid increase in traffic congestion on highways of virtually every large urban area, explain a major portion of the observed deterioration of urban air quality. To halt this deterioration and to secure safe and healthy environments and improve the quality of lifein our cities, it is useful to initiate and implement programs thattreat jointly traffic congestion, air quality, and road safety. Market-based strategies, driven by price mechanisms, have been proposedas the best and most efficient way to decrease traffic congestion and to reduce vehicle emission. Congestion pricing, emission fees, reducing emissions of high-polluting vehicles, and introducing more efficient vehicle and/or fuel technologies are not mutually exclusive strategies and therefore they can be employed jointly within an overall strategy. In view of the conflicting objectives that may exist between improving urban air quality and reducing road fatalities and traffic congestion, it is of great importance to investigate thoroughly these functional relationships. The results of such studies willhelp decision makers identify the "socially optimal level of congestion" that will yield the highest net social benefit. (A)
Abstract