A Connected Vehicle-to-Everything (V2X) System Field Tested in Oakland County, Michigan Reduced Intersection Travel Time by 10 Seconds with Traffic Signal Priority.

METHODOLOGY

Traffic signal priority was first tested in virtual simulations, then field tested at four intersections. VRU test used simulated objects for a real-world intersection. An edge–cloud VRU detection system was developed using intersection cameras and a detection model. Detected VRUs were formatted as SAE J3224 SDSMs and broadcast through the RSU to enable vehicle OBUs to issue driver alerts based on MAP (geometric information) and signal phase and timing (SPaT) data. Both quantitative performance measures, such as intersection traversal time and packet loss over distance, and qualitative feedback were used to evaluate cooperative perception, signal priority, overall system performance, and financial sustainability. The feasibility and security of delivering V2X messages over unlicensed Wi-Fi were also tested.

FINDINGS

• Deployed Stage One prototype demonstrated that V2X system can operate reliably in real-world conditions:
  • Traffic Signal Priority: Based on evaluations with the test vehicle, traffic signal priority provides an approximately 10 second reduction in travel time at an intersection on average each time a vehicle passes through an intersection.
  • VRU detection and alerts: The average end-to-end latency was about 1.8 seconds, with a mean average precision of 48 percent. The latency was primarily caused by the time required for the camera to capture and stream data and was higher than the acceptable threshold of 300 ms.
  • Multi-band communication test: 802.11p (Unlicensed National Information Infrastructure (U-NII)) and Wi-Fi (802.11ac) performed comparably to or better than the 5.9 GHz ITS band, maintaining stable connectivity up to roughly 400 meters.
• Cost saving via Traffic Signal Priority: Based on the American Transportation Research Institute’s reported hourly operating cost of $91.27 for trucking, the estimated cost savings was $0.25 for each traffic signal priority intersection that a vehicle passes through whether traffic signal priority is granted or not. This represented $1,318.34 annual cost saving for one vehicle passing through a 10 equipped intersection corridor, twice per day, for five weekdays.
• The project estimated a 0.4 percent crash reduction (about 187 crashes avoided by V2X technology over three years) would offset project costs (projected at $15 million), demonstrating that V2X safety benefits vastly exceed deployment expenses.