Evaluating the Environmental Benefits of Median Bus Lanes: Microscopic Simulation Approach

Abstract

Median bus lanes are an important element of bus rapid transit (BRT) systems, and can improve traffic operations by separating bus traffic from the traffic in general-purpose lanes. Thus, the operation of BRT systems with dedicated bus lanes is expected to reduce energy consumption and produce positive environmental impacts to a substantial degree. This study attempts to quantify the impacts for a corridor in Seoul, South Korea where frequent bus services are provided, using an integrated simulation tool composed of a microscopic traffic model and a vehicle emissions simulator. This approach has rarely been applied for evaluating the environmental benefits of BRT systems. Given a high volume of bus traffic, the simulation results reveal that corridor energy consumption can be reduced by 18.5% and emissions can be reduced by 1 9.3-31.4%, depending on the pollutant (CO, CO2, PM10, PM2.5, NOx). Vehicles in general-purpose lanes contribute 99.0% of the emissions reductions, with the remaining 1.0% contributed by transit buses. Considering that vehicles in general-purpose lanes represent 94% of corridor traffic, and provide 99.0% of the emission reduction contribution, the simulations suggest that median bus lanes benefit not only the bus operations, but also significantly improve the traffic flow in the general-purpose lanes, contributing to the overall corridor emissions reductions.