Abstract
A reversible roadway (contraflow) is one in which the direction of traffic flow in one or more lanes is reversed to the opposing direction for some period of time. Reversible roadways are most commonly used for accommodating directionally imbalanced traffic associated with daily commuter periods. Reversible lanes also have been widely used, in recent years, for evacuating major metropolitan regions threatened by hurricanes and other disasters. One important problem in the practice of evacuation traffic organization is the choice of road links for contraflow. Most research on the choice of contraflow links does not consider the influence of intersections, which leads to overestimation of evacuation capacity especially in congested urban road networks. We abstract an evacuation road network as a special network with directional node-weights by considering the capacity of intersection movements as directed weights of nodes. We define the critical edge for increasing the maximum flow value of such network as the one that can maximize the range of flow value increase by expanding its capacity. We obtain alternative links for contraflow by searching critical edges in such network. We presented a modified algorithm for finding such critical edges on the basis of the maximal capacity path algorithm for the classical maximum flow problem. We also provided a numerical example and tested the effects through traffic simulation. Our results show that the results considering the influence of intersections are more reasonable than those ignoring it and that taking the intersection effects into account enables us to reduce the total evacuation time.
Highlights
A large area evacuation is usually needed for emergency management in the event of natural or man-made disasters, which produce a dramatic, unbalanced traffic surge
We presented a modified algorithm for finding such critical edges on the basis of the maximal capacity path algorithm for the classical maximum flow problem
We present a modified algorithm for finding such critical edges on the basis of the maximal capacity path algorithm for the classical maximum flow problem
Summary
A large area evacuation is usually needed for emergency management in the event of natural or man-made disasters, which produce a dramatic, unbalanced traffic surge. The first focuses on identifying optimal positions ( called additional intersections) as the starting points to change lane directions in a section of highway This approach is mainly applied to hurricane related evacuations. We propose an improved critical edge model of the maximum flow to optimize the link selection for contraflow. By abstracting the evacuation network as a special network with directional node weights and searching for the critical edge of maximum flow increase in it, the alternative road links suitable for contraflow can be obtained when the influence of intersection is taken into account. Based on the above considerations, we consider the optimization of the reversal links selection as the critical edge problem of the maximum flow increase in the network with directional node weights. One or more links can be selected to expand the capacity through contraflow according to the real evacuation demand, with the expectation that the overall evacuation capacity of the road network will be improved
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