Development of a Deployment Planning Tool for Freeway Safety Service Patrol Programs

摘要

Many transportation agencies take part in the freeway incident management process by deploying safety service patrols (SSPs), typically on highly congested, urban roadways. SSPs are a countermeasure to freeway operations problems, and their implementation can improve safety and mitigate nonrecurring congestion. They are typically deployed in areas that have high traffic volumes (e.g., urban freeways) and are charged with clearing obstructions from roadways such as debris and disabled vehicles as well as assisting state police with traffic control at crash scenes. Although patrols continue to expand throughout the nation, deployment criteria have remained relatively unchanged; for example., deployment is often driven by congestion patterns in major metropolitan areas. In view of the relatively limited factors used for deployment decisions, a few SSP programs have deemed it necessary to develop empirically driven deployment criteria to help guide decision-makers in making sound, data-driven investment decisions. The purpose of this study was to develop a deployment planning tool that would help transportation agency decision-makers when considering expanding SSP coverage and/or altering existing route coverage. Data obtained from SSPs operating in Virginia were used to develop the planning tool, which is a segment-based ranking scheme that can be applied to rural and urban freeway segments. Within the tool an SSP-assist prediction model was developed to predict incidents statistically using average annual daily traffic, segment length, average daily percent of ADT served, and truck percentage. The tool was validated on existing SSP routes and the results concur with those obtained in recent operations-level studies.