Intelligent Work Zone Using Automatic Queue Detection Systems

This report documents the the evaluation of the effectiveness of the Advanced Queue Detection (AQD) systems installed on Interstate work zones in Nebraska. Specifically, (1) the system performance was verified by examining whether the messages displayed on the portable dynamic message signs (PDMS) were consistent with the underlying AQD logic; (2) the system efficacy was measured by determining whether driver speeds were reduced when warning messages were provided on the PDMS; and (3) the system safety impact was modeled using statistical models. It was found that overall, the AQD systems had an error rate of 0.7% – 2.3%. Drivers reduced their speeds in response to the PDMS warning message, and the decrease was found to be statistically significant in the range of 3.5 to 7 mph. This was approximately 90% greater than the reduction in speed that occurred when the PDMS did not display any message. In summary, it was found that the AQD systems were operating correctly and, more importantly, they were effective in reducing the space mean speeds of vehicles approaching work zones. Results from the traffic crash analysis showed that most crashes occurred in the activity area of the work zone and were rear-ended. A crash was more likely to occur on weekdays, off-peak hour, in the daytime, no worker present at rural Interstate work zones. A crash was severer when drivers driving drunk, during the daytime, on weekdays, with more vehicles involved. Given that the data was obtained in the midst of the COVID-19 pandemic, its impact on the work zone traffic crashes were also studied.