Differential variable speed limit control strategy consider lane assignment at the freeway lane drop bottleneck

Reduction in the number of lanes (lane drop) is typical on freeways due to road design, incidents, or road maintenance. As traffic demand increases, the bottleneck becomes activated because of there are many of vehicle lane-changing behaviors at the bottleneck. At the same time, the traffic density increases, resulting in a capacity drop phenomenon at the bottleneck. The degree of the capacity drop is also closely related to the traffic density at the bottleneck. Variable Speed Limit (VSL) is a widely used Active Traffic Management (ATM) method. In traditional research, most VSL control strategies consider all lanes uniformly and set uniform dynamic speed limits. However, traffic varies by lane. This study proposed a differential variable speed limit (DVSL) control strategy for each lane considering lane assignment. The DVSL control strategy sets the dynamic speed limit for each lane to attract a certain number of vehicles to change lanes before the bottleneck and reduce the impact of traffic capacity drop. This strategy is simulated based on extending the cell transmission model (CTM) to multi-lane. The multi-level iterative optimization algorithm obtains each lane's dynamic speed limit values. The experimental results show that the proposed DVSL control strategy can alleviate traffic congestion and improve efficiency. Total travel time (TTT) improved by 7.48 % compared to the no-control measures.