An integrated traffic control policy for incidents in freeway-arterial corridors

Date of Completion

January 1997


Engineering, Civil




When unexpected congestion occurs on a freeway, diverting vehicles from the freeway to a less congested arterial is a common solution for mitigating the problem. However, diverting traffic without appropriately modifying traffic control on the alternate routes simply transfers the congestion problem from the freeway to these routes, which often are local streets.^ This study investigates the impact of diverted freeway traffic on a typical local street network under different incident scenarios and to learn how to select optimal control strategies. New timing plans are developed for the arterial network using PASSER-II to optimize signals on the alternate route for both one-way and two-way progression schemes with various levels of proposed diverted freeway traffic to explicitly serve traffic diverting around a freeway incident. Evaluation of these timing plans including measurements of delay and progression bandwidth are compared for various control strategies.^ Operations in the network are then simulated with above developed timing plans and various incident scenarios to investigate how these plans affect corridor performance during different types of incidents at various freeway traffic demand levels. The integrated network simulation program INTEGRATION$\sp\copyright$ is used for this analysis. Measures of effectiveness (MOE's) including the average network speed for the entire corridor (the freeway system and the surrounding street network), the link speed for selected links and the travel time for two diversion routes on the arterial network are compared with respect to operation for each timing plan and incident scenario. The results of additional intermediates freeway traffic demand levels are examined for the most sensitive range of above design variables.^ This research into mitigating congestion during freeway incidents addresses performance in an entire corridor under different freeway diversion and arterial signal coordination strategies, not just on the freeway. It also identifies relationships among traffic network characteristics, traffic control plans, and incident characteristics, thus providing important insights into optimizing the trade-off between congestion on freeways and surface streets. ^