Target Completion Date: July 31, 2023 Safety, Operations, and Traffic Engineering
The Virginia Department of Transportation is currently using the simple ranking method as their primary screening method for segments. While straightforward in implementation, the simple ranking method is prone to extreme segment length variation if applied directly. To be more specific, it was found that very short segments (< 0.01 miles) used in network screening resulted in high randomness in terms of the selection of high-risk sites, and the use of very short segments induced the Safety Performance Factor (SPF) model to be more sensitive to errors in locations and may have a dramatic effect on model performance. The Traffic Engineering Division acknowledged the short-segment issue and grouped those short segments with neighboring ones to mitigate the issue. The Traffic Engineering Division also initiated a technical assistance study (Virginia Transportation Research Council Technical Assistance: Evaluation of Segment Length in Network Screening Safety Analysis), which determined that the sliding window screening method and the use of Average Annual Daily Traffic (AADT)-clustered links showed some promising properties in the development of SPFs on Interstate networks. Following up the prior technical assistance study, the purpose of this project is to (1) develop the AADT-clustered segmentation method including multiple facility types on the Virginia roadway network, (2) develop the Highway Safety Manual’s recommended sliding window screening method with the developed AADT-clustered roadway network and compare with the current simple ranking method’s result, and (3) document the data prerequisites, preprocessing procedures, and the strengths and limitations of those methods.
Last updated: December 8, 2023
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