This paper examines temporal, spatial and modal effects of second-best congestion pricing schemes in traffic volume reallocation, traffic mode shifting and automobiles toxic pollutants emission control in urban road systems. A problem in two time periods (peak and off-peak) and two travel modes (private car and bus) on one-way network is analysed, and a second-best congestion pricing model with multiple time periods and travel modes is constructed using an excess-demand approach. The paper provides a thorough empirical study of second-best scenario and two extreme regimes: no-toll problem and first-best problem. The main findings are: congestion pricing policies have major impacts: 1) diversion of tolled route to the free route; 2) shift of peak period traffic to the off-peak period; 3) shift of traffic volume by private car to bus; 4) reduction in total traffic volume and increase in total passenger volume (private car and bus); 5) reduction in the total emission amount of automobiles’ toxic pollutants.
Keywords: environmental pollution, urban highway, congestion pricing, second-best, elastic demand, automobiles’ toxic pollutants