Implementation of Active Traffic Management Strategies for Safety on Congested Expressway Weaving Segments

Abstract

In weaving segments, traffic merges, diverges, and weaves in a limited space. These traffic maneuvers might result in high crash hazards. To improve the safety of a congested expressway weaving segment, this study tested various active traffic management (ATM) strategies in microsimulations. Crash odds and the Surrogate Safety Assessment Model were used to evaluate the impact of ATM strategies on traffic safety. The crash odds were calculated based on the real-time safety analysis model for weaving segments. The strategies included ramp metering (RM), variable speed limit (VSL), and integrated RM and VSL (RM-VSL). Overall, the results showed that the ATM strategies improved the safety of the studied weaving segment. The modified ALINEA RM algorithms, which took lane occupancy and safety into consideration, outperformed the traditional ALINEA algorithm from a safety perspective. The 45 mph VSLs, which were located at the upstream of the studied weaving segment, significantly enhanced safety without notably increasing average travel time. A consolidated RM-VSL strategy was also proposed with the aim of improving traffic safety by implementing RM and VSL. In the consolidated RM-VSL strategy, the modified ALINEA RM was adjusted according to the queue length to prevent long queues on ramps. The results proved that the consolidated RM-VSL strategy reduced the number of conflicts by 16.8% and decreased the crash odds by 6.0%.