PennDOT Virtual Queue Detection System Reduced Crashes by 11 Percent Annually and Truck-Related Fatal Crashes by 50 Percent.
Providing Drivers with Better Information Regarding Traffic Conditions Resulted in Crash Frequency and Safety Benefits on 11 Corridors Across Pennsylvania.
Statewide, Pennsylvania, United States
Virtual Queue Protection Corridors
Summary Information
The Pennsylvania Department of Transportation (PennDOT) identified crashes occurring in congestion as a significant issue on the state’s core roadway network, specifically crashes where drivers unexpectedly encounter a queue. A solution was needed to automatically warn drivers of impending queues without relying on manual updates to message signs or the deployment of physical sensors. The agency determined that it could implement virtual queue protection corridors in areas where changeable message signs (CMS) were already present using speed data integrated in their Advanced Traffic Management System (ATMS).
METHODOLOGY
PennDOT collaborated with its ATMS vendor to develop a corridors module for the system, which included geofencing the corridor extents and identifying the CMSs within each corridor. Traffic speeds within a corridor were monitored by segments, and when speeds dropped below a defined threshold, warning messages about queuing ahead were automatically posted to upstream signs. In late 2022 and throughout 2023, PennDOT implemented 18 queue protection corridors covering 600 miles statewide. Feedback from Engineering District Traffic Units and Traffic Management Centers led to system improvements; for example, the priority of the queue warning messages was adjusted to allow any critical messages regarding commercial vehicle restrictions to take precedent.
FINDINGS
PennDOT analyzed safety data from 11 queue protection corridors as of April 2024:
- Total crashes decreased from 1,808 crashes per year prior to activation to 1,625 crashes per year following activation (an 11 percent reduction).
- Rear-end crashes involving trucks were reduced by 13 percent and fatal crashes involving trucks were reduced by nearly 50 percent (from 13 to 7).
- Passenger vehicles only saw a slight reduction in fatal crashes.
- Fatal and injury crashes dropped by over 20 percent in one-third of the corridors.
- Drivers saved approximately 72,116 hours of travel time in the year post-activation (109,088 person-hours when accounting for occupancy rates). This included 10,075 hours of travel time savings for trucks.
- The 183 per year-crash and associated injury severity reduction represents an estimated total annual savings of $53.4 million.
- Monetizing the travel time savings, motorists saved $2.2 million in the year following the activation.
- Operational savings (e.g., fuel, oil, tires, maintenance and repair, vehicle depreciation) totaled nearly $300,000 a year, including over $100,000 for trucks.
