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

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 19.3–31.4%, 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.