Intelligent Work Zones Utilizing Portable Warning Messages were Found to be Effective in Reducing Driver Speeds at Four Work Zone Sites in Nebraska.
Intelligent work zones have been increasingly recognized across the United States due to their proven role in improving traffic safety and operations. For example, Advanced Queue Detection (AQD) systems, which measure work zone-related queuing in real-time, inform drivers upstream so they can be prepared to slowdown or stop. This study evaluated the performance and efficacy of the AQD systems installed at four work zones along Interstate 80 in Nebraska, by determining whether driver speeds were reduced when warning messages were provided on the Portable Dynamic Message Signs (PDMS). Data pertaining to work zone AQD systems from Fall 2020 and Summer 2021 were utilized.
In this study, portable traffic data capturing units, consisting of cameras and Wi-Fi receivers as detectors, were utilized through a private company. Cameras within the portable units were used to obtain video data of traffic traversing the roadway. The Wi-Fi receivers were used to capture Media Access Control (MAC) addresses, and their associated time stamps, from passing vehicles. Travel time data collection was conducted in two phases; first phase was during September through November in 2020, and the second phase was in July 2021, at the four work zone test sites located in Waco-Utica, Big Springs (has two sites), and Ogallala, NE. The system's performance, efficacy, and safety impact were evaluated by checking message consistency with the AQD logic, assessing speed reduction when warning messages were displayed on the PDMS, and employing statistical models respectively. Results were reported for the two sites in Waco-Utica and Big Springs as slow-moving traffic was observed at these work zones.
- It was found that drivers reduced their speeds in response to the PDMS warning messages, and the reductions were statistically significant.
- Specifically, under the warning scenario, the speed reductions at a particular segment were 7.0 mph and 3.5 mph at Waco-Utica and Big Springs, respectively.
- These reductions were, on average, 90 percent greater than the speed reductions of 3.6 mph and 1.9 mph compared to the same segments under the scenario where the PDMS did not display a warning message.