Fault-tolerant variable speed limit control for freeway work zone

Freeway work zone can easily lead to traffic congestion which has detrimental effects on travel time and safety. By using the detected traffic states near work zone area, variable speed limit (VSL) control system has been widely studied to improve traffic mobility and safety. However, occurrence of sensor fault can cause traffic state deviation and system degradation. Therefore, this study presents a fault-tolerant VSL control system for freeway work zone. A traffic flow model was first designed to analyze the traffic dynamics. Then a sliding mode controller for VSL was designed based on the previous study. By comparing the estimated traffic states from Kalman filter with the observed states from the observer, the developed fault diagnosis can detect the sensor fault and reconfigure the controller. The proposed system was evaluated under a realistic freeway work zone environment in traffic simulator SUMO. The results show the proposed system can achieve fault tolerance and improve traffic mobility and safety under fault-free and sensor-fault scenarios.