To promote smoother freeway traffic flow during evacuations, ramps may be closed and thus reduce the number of merging and related speed reduction points. Deciding which ramps to close can be treated as an optimization problem in which the decision variables are integers that indicate whether the ramp is open or closed. This paper examines the problem under multiple demand and budget scenarios for no-notice evacuations. Through the optimization formulation and solution method, optimized closure plans are developed for each scenario and compared with the do-nothing case, and an existing plan is developed with professional judgment. The optimized plans outperform the others in the evacuees' total travel time but are sometimes associated with decreases in overall network throughput. Three ramp closures, consistent across the scenarios, are explored as a reduced closure plan, and evacuee benefits are identified for all of the scenarios over the do-nothing option except in the most congested background traffic scenario. However, even in the most congested case, the three-ramp closure plan improved evacuees' travel times over the plan developed without analytical and simulation support. Although the exact optimized ramp closure plan varies across scenarios and budgets, overlap of the plans can help generate a smaller closure plan that provides benefits over plans that are strictly judgment based and over the do-nothing option in less congested cases.
ASJC Scopus subject areas
- Civil and Structural Engineering
- Mechanical Engineering