The effects of a traffic guidance scheme for auto-toll lanes on traffic safety at toll plazas

The Transport Department of the Hong Kong SAR government conducted a trial traffic guidance scheme at the plaza of a busy road tunnel. The scheme involves the placing of reflective road markings on the approach lanes to the toll plaza and the erection of a gantry sign that clearly distinguishes the auto-toll lane. The main purpose of the scheme is to improve traffic flow and traffic safety at the toll plaza. If the scheme is successful, then it will be applied to all other toll plazas in Hong Kong. We conducted an observational before-and-after study to assess the effects of the scheme. We found that the overall lane-changing rate decreased significantly by 23% (0.1 lane crossings per vehicle) at a significance level of 0.05, the pooled conflict count decreased sharply by 44% at a significance level of 0.10, and the crash count also decreased sharply by 38%. The mean travel time for non-auto-toll traffic increased significantly by 30% (8 s), whereas that of auto-toll Sunday traffic decreased by 18% (2 s). Both changes are statistically significant at a level of 0.05. The results indicate that the trial scheme provided good guidance to drivers. Traffic safety was improved, and the travel time of auto-toll traffic improved in certain periods, although at the expense of non-auto-toll traffic.