Evaluation of Temporary Ramp Metering for Work Zones

Ramp metering has been successfully implemented in many states to improve traffic operations on freeways. Studies have documented the positive mobility and safety benefits of ramp metering. However, there have been no studies on the use of ramp metering for work zones. This paper reports the results from the first deployment of temporary ramp meters in work zones in the United States. Temporary ramp meters were deployed at seven work zones in Missouri. Safety measures such as driver compliance, merging behavior, speed differentials, lane changing, and braking maneuvers were extracted from video-based field data. Mobility analysis was conducted with a calibrated simulation model, and the total delays were obtained for under capacity, at capacity, and over capacity conditions. This evaluation suggests that temporary ramp meters should be deployed only at work zone locations where there is potential for congestion and turned on only during periods of high congestion. The compliance analysis showed that noncompliance could be a major safety issue in the deployment of temporary ramp meters. The use of a three-section instead of a traditional two-section signal head for ramp metering produced significantly higher compliance rates. Mobility analysis revealed that ramp metering produced delay savings for high traffic volume work zones. For flows below capacity, ramp metering is not recommended because it increases total delays.