Roadwork that results in a lane closure can reduce both the safety and efficiency of a roadway. The dynamic merge is a form of merge control designed to mitigate the potential hazards of lane closures by customizing the merge environment to suit the current level of traffic. When traffic is light, early merge signs encourages drivers to merge into the open lane prior to queue formation. When traffic is heavy, late merge signs encourages drivers to remain in the closed lane for as long as possible. The current study used a driving simulator to assess the independent effects of traffic volume and dynamic merge messaging on merge location and traffic throughput. Merge location was influenced by merge environment, such that drivers in the early merge condition merged earlier than those in the late merge condition regardless of traffic volume. In addition, when traffic was heavy, participants in the late merge condition passed through the work zone more quickly than those in the early merge condition. The results are suggestive of the beneficial effects of the late merge on traffic throughput and the effectiveness of the dynamic merge messaging in influencing merging behavior.