About me
How a new metro line influences local traffic safety: A natural experiment in China
Urban rail transit systems, in particular metro, have experienced unprecedented expansion in developing countries over the past decades. The introduction of a new rail transit system is expected to transform the travel behaviours of urban residents and alleviate traffic congestion in station areas. However, the causal impact of the rail transit system on traffic safety is theoretically debatable, and the empirical evidence is limited. Leveraging a new metro line in a large Chinese city and longitudinal traffic crash datasets covering before and after metro operation stages, this study provided causal evidence regarding how a new metro system affects traffic crashes in the vicinity of metro stations, including overall injurious crashes, pedestrian-involved, automobile-involved, and electric bicycle-involved crashes. This study integrated local contextual knowledge and assigned treatment and control groups to provide rigorous evidence. Treatment groups were the areas that experienced new metro service recently, and control groups were assigned to areas with planned metro lines and similar built environment attributes. Difference-in-differences (DID) models showed that the new metro line increased overall and pedestrian-involved crashes compared with the control groups after the metro operation. However, significant overall treatment effects on automobile-involved and electric bike-involved crashes were not observed. In addition, the treatment effects of the metro intervention on traffic crashes varied with the station location and the safety risk level before intervention. Our findings provided causal evidence contributing to the ongoing debates on the traffic safety implications of rail transit interventions and support the development of safer, integrated transportation and urban planning in high-density contexts.
