Safety assessment of freeway merging and diverging influence areas based on conflict analysis of simulated traffic

The safety of merging and diverging influence areas, intersections, interchanges, and other traffic facilities is assessed by tracking and analyzing police-reported motor vehicle crash records. Since the nature of road crashes is random and infrequent, this process is slow to reveal the need for remediation of the roadway design and traffic control strategy. Moreover, this process is not applicable to assess new designs that have not yet been built, or deployed in the real world.;This study summarizes a technique combining micro-simulation and automated conflict analysis to assess the safety of traffic facilities without waiting for a statistically above-normal number of crashes to occur. The technique is also valuable in assessing the relative performance of one design versus another. Traffic Conflict Technique (TCT) is among the most common surrogate measures to study the safety of roadway facilities. The software referred to as Surrogate Safety Assessment Model (SSAM) was developed by FHWA and was used in this study. The SSAM software application was designed to perform statistical analysis of vehicle trajectory data. Trajectory data is the output from microscopic traffic simulation models. Among the various traffic simulation modeling tools, VISSIM was chosen because of its compatibility with SSAM, its versatility for analyzing networks of big sizes and its ability to provide users with the capability to model any type of geometric configurations.;Forty-two merging and forty-two diverging influence areas in Colorado, USA, were modeled in VISSM and conflict analysis was performed using SSAM under AM-peak traffic conditions. Five field validation tests were conducted. Conflicts predicted by SSAM approach were compared with actual crash records at merging and diverging influence areas in all statistical validation tests. The results of the validation effort of safety assessment based on conflict analysis of simulated traffic suggested that this technique is recommended for safety assessment at merging and diverging locations.