Study of Smart Work Zone Speed Notification System Deployed in Minnesota Evaluated the Impacts on Vehicles Approaching Queues.
A Smart Work Zone Speed Notification (SWZSN) system aims to reduce congestion, queuing, and rear end crashes in work zones by informing drivers of downstream segment speed. The system uses an Intelligent Lane Control System (ILCS) and Portable Changeable Message Signs (PCMS). The SWZSN system was installed at nine stations along a 4.4-mile segment of I-94 in St. Paul, Minnesota in Spring 2016. Video footage was collected from Spring 2016 to Fall 2017 to support the evaluation, using computer vision to extract vehicle trajectory data. A regression analysis used calculated vehicle deceleration rates, detector speed data, and PCMS message logs to examine the effects of various combinations of sign messages and starting speeds on driver deceleration rates.
Overall, the SWZSN system led to mixed traffic safety results. The key finding from the study was that the system is noticed by drivers and resulted in a statistically significant influence on driving behavior.
- Use downstream speed notification, as opposed to displaying advisory speed limits, for effective traffic control.
- Using temporary detection on portable trailers rather than trying to utilize the permanent detectors allows for greater flexibility in detector placement to avoid obstructions caused by the work zone, or placement in more strategic locations where queues developed.
- Test and refine a new smart work zone system on a simpler construction project before trying to test it on one with complicated staging plans and traffic separated by multiple concrete barriers.
- Display clear and accurate messages (e.g., “Stopped Traffic Ahead” or “15 MPH ½ Mile Ahead”) to increase positive effects on driver attention.
- Minimize speed notification system usage when there are no significant capacity reductions, since this may reduce driver attention.
- Use work zone speed notification systems as a queue warning system under regular traffic conditions.
- Improve speed estimation and message generation to reduce the occurrences of misleading and counterproductive message combinations.