Road Safety Audits and major P-3 freeway projects: estimating the reduction in collision frequencies

Road Safety Audits (RSAs) include an independent review process that has increasingly been incorporated into the Design-Build-Operate model for (typically) large-scale freeway construction projects throughout Canada. While recent research has suggested that RSAs are a cost-effective means to improve safety on freeway (and other road) facilities, empirical evidence is lacking. This study undertook a comparison of observed and predicted collision frequencies from three large-scale Public-Private- Partnership (P-3) rural freeway projects with similar fundamental characteristics (e.g., functional classification, cross-sectional geometry, RSA team, and project budget). Collision reductions associated with the RSA process were estimated to develop a better understanding of the net safety impacts that may be attributed to the review process. The study results indicate that including RSAs in the development process of the freeway projects has reduced the overall frequency of collisions by 15% (or a collision modification factor of 0.85), which is equivalent to a reduction of 0.12 collisions per kilometre per year.