Freeway Bottleneck Simulation,Implementation,and Evaluation

A fully documented case of problem identification, simulation, implementation, and evaluation has been developed for freeway bottleneck congestion mitigation. The benefits of using simulation for assessing improvement scenarios of a congestion-generating merge between two freeways and an on-ramp in the central part of Attica Tollway in Athens, Greece, are presented. The best feasible alternative identified by two simulation programs, Integration and VisSim, was constructed, and before and after field and simulation results are available. Only 16 months passed between the initial data collection for bottleneck analysis and the 2 months of evaluation with the constructed improvement, thereby minimizing large temporal and other exogenous factors. As a result of conservative simulation assumptions, larger than forecast improvements in speed, travel times, and queue reduction were realized. The two simulators, however, provided reasonable and comparable measures of performance, which were instrumental in the decision to construct the proposed improvement.