Freeway service patrols (FSPs), classified as part of intelligent transportation systems, are programs that use roving vehicles to patrol congested and high-incident sections of freeways; they help to smooth traffic flow by aiding stranded motorists and assisting in incident clearance. Many major urban areas currently have patrols, and most medium-sized urban areas are following suit. The success of FSPs has resulted in frequent requests for service expansion. However, the decision on where to put the next patrol is becoming more difficult because an assessment of greatest need typically indicates that high-priority areas already have the service, whereas the possible effects of the service are often indistinguishable on lower-priority facilities. A new approach was developed to help determine the most beneficial locations for patrol deployment by using expanded placement criteria. North Carolina was used as a case study. Analysis of three incident and crash indexes was combined with spatial analysis, incident type distributions, average hourly freeway traffic volumes, and incident delay estimations to identify, evaluate, and compare candidate facilities for FSP expansion.
Results of the research were incorporated into a decision support tool that allows easy planning and operational assessment of candidate sites by comparing performance values between sites, modeling the effect of FSPs, and estimating their key potential benefits. By using the tool, decision makers can quickly assess the needs of different facilities and make an informed, cost-effective decision on where to implement the next service patrol.
Khattak, A., N. Rouphail, K. Monast, and J. Havel. Method for Priority-Ranking and Expanding Freeway Service Patrols. In Transportation Research Record: Journal of the Transportation Research Board, No. 1867, Transportation Research Board, National Research Council, Washington, D.C., 2004, pp. 1-10