Discussion of “Queue Storage Design for Metered On-Ramps” by Zhongren Wang

This article presented a discussion on a research paper entitled “Queue Storage Design for Metered On-Ramps”, published by the International Journal of Transportation Science and Technology on March 2013 (Volume 2, Issue 1, Pages 47–63). This discussion first summarized the contributions of the paper under discussion, and emphasized a critical insight presented by the paper under discussion that designing queue storage length as a percentage of peak hour on-ramp demand. Then, this article discussed the potential factors that may affect queue length estimation results, including different traffic flow arrival patterns between arterial-to-freeway ramps and freeway-to-freeway connectors, queue length as a function of demand-to-capacity ratio instead of on-ramp traffic volume, and errors caused by the stochastic nature of traffic flow when using field measured queues. Lastly, this article outlined methods to solve these limitations, and presented preliminary insights into the development of metered on-ramp queue storage length design guidelines considering the impacts of ramp geometric features and signal timing schemes of the upstream intersection.