Impact of Bottleneck Merge Control Strategies on Freeway Level of Service

Freeway work zones typically mandate lane closures that often induce bottlenecks. Merge maneuvers and the accompanying increase in the rate of lane changes at these bottlenecks can become problematic resulting in undesirable mobility and safety impacts. Traditionally, merge control strategies are deployed to mitigate such impacts. Literature sources indicate that available merge control strategies fall into one of four categories, namely: (i) early merge control, (ii) late merge control, (iii) temporary ramp metering, and (iv) mainline merge metering. However, little is known about the proper criteria for selecting and implementing one of the available merge control strategies. In addition, the impact of the various control strategies on freeway Level of Service (LOS) is currently under-researched. The purpose of this study is to evaluate the operational impacts of the above-mentioned freeway merge control strategies. The goal is to provide work-zone-aware LOS indicators that would help transportation agencies in selecting the most appropriate merge control strategy to minimally impact the freeway operations. In order to meet the research goals and objectives, this study used the CORSIM micro-simulation platform to evaluate impacts of various merge control strategies at a freeway study corridor in Birmingham, AL. The 2010 Highway Capacity Manual methods for calculating LOS were considered and modifications were proposed to align the calculated LOS with the assessed impacts of each merge control strategy. This study is significant for its contribution to providing transportation researchers and professionals with tools and methods to evaluate freeway LOS under work zone conditions and assisting them in mitigating the adverse impacts of work zones on traffic operations.