Crash analysis of Chinese freeway tunnel groups using a five-zone analytic approach

For mountainous freeways, some tunnels are situated adjacent to each other resulting in the tunnel group. This study aims to investigate the characteristics of traffic crashes in freeway tunnel groups. A typical mountainous freeway with tunnel groups in China is studied using police-reported crash data. A five-zone approach is proposed for safety analysis of tunnel groups. The result shows that the connection zone has the highest crash rate. Interior entrance zone has a significantly higher proportion of crashes during the daytime compared with other four zones, while the exit impact zone is associated with a higher proportion of crashes during the nighttime. This indicates that crashes are more likely to occur when a vehicle moves from bright to dark environments. Findings in this study shed some light on the engineering and policy implications for raising traffic safety of freeway tunnel groups.