Exploring the Effectiveness of Variable Speed Limit Controls on Highway Work-Zone Operations

Abstract

Despite the well recognized fact that a proper control of traffic speed can contribute to both reduction in accidents and efficiency of highway operations, most existing strategies for work-zone speed control in either Europe or the U.S. tend to primarily focus on improving traffic safety. This article presents two online algorithms for variable speed limit (VSL) controls at highway work zones that can take full advantage of all dynamic functions and concurrently achieve the objectives of queue reduction or throughput maximization. To evaluate the effectiveness of these proposed algorithms, this study has conducted extensive experiments based on simulated highway systems that have been calibrated with field data. The results of these simulation analyses have confirmed that VSL algorithms can yield a substantial increase in both work-zone throughputs and reduction in total vehicle delays. Moreover, traffic flows implementing VSL controls tend to exhibit lower speed variances than other non-controlled traffic scenarios. The speed variance reduction may indirectly contribute to improving the overall traffic safety in work zones.