Evaluating the environmental impact of bus signal priority at intersections under hybrid energy consumption conditions

Abstract

The acceleration of the motorization process creates severe environmental problems by affecting the energy consumption of urban trafic. As a major source of trafic pollution, vehicle exhaust deserves more attention when making trafic policy. Actually, the acceleration, deceleration, and idling conditions of vehicles cause more pollution than usual, which mainly happens at intersections of the road network. Besides, in the context of giving priority on public transport development, bus signal priority (BSP) at intersections becomes a quite prevalent measure to reduce average capita delay for travelers, while long-term practice also indicates that the unreasonable setting of bus lane further worsens the running conditions for other vehicles by occupying excessive trafic capacity, which highlights the indirect environmental effects of BSP. This paper provides a simulation-based method for evaluating the adaptability of BSP to find an optimum balance between eficient and environmental care. Specifically, the trafic volume, bus mixed rate of the intersection and energy types of vehicles consist of hybrid energy consumption conditions collectively. A VSP (vehicle specific power)-based exhaust emission models for both buses and other vehicles are employed to estimate the environmental cost of the entire intersection. Moreover, the overall eficiency of gasoline and electric vehicles is further evaluated to offer more implications for trafic control practice.