Evaluation of Integrated Variable Speed Limit and Lane Change Control for Highway Traffic Flow

Abstract

A sudden lane drop on a freeway with high volume of vehicles can cause severe traffic congestion and safety issues. Forced lane changes near the bottleneck reduce the traffic mobility on all lanes and trigger the capacity drop phenomenon. Numerous studies have explored the effect of Variable Speed Limit (VSL) and Lane Change (LC) control on solving the bottleneck congestion, but only a few have taken the measurement or model uncertainties into considerations. In this paper, we design an integrated VSL and LC controller based on a modified multi-section Cell Transmission Model (CTM) to alleviate the freeway bottleneck congestion and reject uncertainties. The location of the most upstream speed sign is treated as a parameter and optimized using simulation data. We first evaluate the proposed controller without uncertainty to demonstrate its effectiveness in improving traffic flow. Then we incorporate the uncertainties in measurements and model parameters to examine the robustness of the control. The proposed combined VSL and LC controllers are demonstrated to be robust with respect to uncertainties. The bounds of allowable uncertainties are more sensitive when uncertainties lead to a reduction of speed limit commands than an increase.