Development of a Potential for Safety Improvement Index

Advanced statistical methods aimed at identifying high risk sites and ranking locations for investigation using prospective cost effectiveness of potential safety treatments strongly depend on accident data. Unfortunately, the quantity and quality of accident data may be poor and there are important accident contributory factors that in some instances cannot be extracted from the collision statistics. To overcome these drawbacks, a new approach aimed at assessing a potential for safety improvement index basing on both accident data and safety inspection of existing roads is presented. The procedure for assessing the potential for safety improvement index is based on two key elements: accident patterns which highlight road features as a potential accident contributory factor susceptible to correction are analyzed and quantified, road features and road environment analysis identifies if engineering improvement opportunities exist and allows to evaluate how much these safety countermeasures can reduce accident frequency and severity. By combining these two clues, namely accident patterns and road features potentially detrimental to safety, the procedure ensures the chance to assess the PSI index even if specific accident data referred to the road under examination are not available, ensures the chance to assess the PSI index even if exact traffic and geometric data are not available, ensures that the PSI index can be assessed as part of the safety review process without relevant supplementary work and points out safety concerns that can give rise the greatest safety improvements.