Simulation Analysis of Route Diversion Strategies for Freeway Incident Management: Final Report

Abstract

Freeway incident management has become an important issue in departments of transportation nationwide. With many of the nation's roadways operating very close to capacity under the best of conditions, the need to reduce the impact of incident-related congestion has become critical. One way to achieve this reduction is to improve the management of traffic after an incident has occurred, including the use of traffic diversion strategies. Very often, however, diversion strategies are employed without proper consideration given to the effect of such a strategy on the alternate route, which in many cases is congested prior to the addition of diverted traffic. Careful analysis of diversion strategies, which includes examinations of the operational characteristics of both the freeway and alternate routes, can lead to much more efficient and effective strategies. This project establishes a methodology for analyzing diversion strategies using CORSIM, a microscopic simulation model developed by the Federal Highway Administration capable of simultaneously analyzing freeway and arterial roadways. The model process for incident specification and simulation was tested and applied to several case studies. The results of the study show that the model is a valuable tool in analyzing diversion strategies; the critical freeway volume at which diversion becomes advantageous can be determined, as can bottleneck locations on the alternate routes. Signal timing adjustments can be tested and fine-tuned to achieve the ideal maximum flow along the diversion route.