In metropolitan areas, public transportation has been encouraged as a sustainable mode because they can effectively transport many people and have less impact on traffic congestion and environment. In order to increase public transportation ridership, many jurisdictions have attempted to provide improved travel time and reliability of the public transportation system. These efforts include installing transit signal priority, dedicated median/curb bus lanes, bus rapid transit, bus bypass shoulder lanes, et cetera. In Korea, dedicated median bus lanes have been installed and operated since 1996. Currently, approximately 116km of the dedicated median bus lanes on 38 corridors are operational. The implementation of the dedicated median bus lanes in Seoul Metropolitan Area have been successful as they it resulted in the increased travel speed (15 km/h to 19km/h), bus arrival time accuracy (±1 min to 2 min), and daily bus-ridership (from 5.6 million to 5.75 million).

Although there have been several studies that evaluated the operational effectiveness of the exclusive bus lanes in Seoul, few studies have assessed the safety impacts. This study aims at estimating the impacts of implementing median bus lane system in Seoul Metropolitan Areas for vehicle-to-vehicle and vehicle-to-pedestrian crashes. In order to achieve the objective, a before-and-after study with comparison group method was employed and estimated crash modification factors (CMFs).