Methods for Identifying High Collision Concentration Locations (HCCL) for Potential Safety Improvement Phase II: Evaluation of Alternative Methods for Identifying HCCL

摘要

One of the first steps in effectively managing a road network is to identify sites that require safety investigations. It is important that the identification process is efficient, otherwise scarce resources may be wasted on sites that are incorrectly identified as collision concentration sites while roadway locations with a truly high potential for cost-effective safety improvement may not be flagged in this process. Conventional methods that make use of just collision counts or collision rates (per unit of exposure) are now known to have problems because they do not effectively account for the potential bias due to regression-to-the-mean phenomenon in which sites with a randomly high account could be incorrectly identified as having a high potential for improvement, and vice versa. Another problem with conventional methods that make use of collision rates is the implicit assumption that collision frequency and traffic volume are linearly related. Many recent studies have shown that the relationship between collisions and volume depends on the type of facility but tends to be non-linear.