The continuous rapid growth in Vehicle Miles Travelled (VMT), 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. In order to (1) halt this deterioration process, (2) secure safe and healthy environments, and (3) improve the quality of life in cities, it is paramount to initiate and implement programmes which jointly treat (i) traffic congestion, (ii) air quality, and (iii) road safety. A host of market-based strategies, driven by price mechanisms, have been proposed as the best and most efficient way to decrease both traffic congestion and vehicle emission. Strategies such as (a) congestion pricing, (b) emission fees, (c) reducing emissions of high polluting vehicles, and (d) introducing more efficient vehicle and fuel technologies, are not mutually exclusive. Therefore, they can be employed jointly within an overall strategy. In view of the conflicting objectives which may exist between improving urban air quality and reducing road fatalities and traffic congestion, it is of great importance to thoroughly investigate these functional relationships. The results of such studies will help decision makers identify the "socially optimal level of congestion" which will yield the highest net social benefit.
Abstract