Performance Evaluation of Different Detection Technologies for Signalized Intersections in Minnesota

Project summary:

This project evaluated the performance of non-intrusive detection technologies (NITs) for traffic signals in Minnesota. Prior work shows that while no single NIT device performs best in all situations, under specific circumstances, some NIT devices consistently outperform others. The team's goal in this project was to determine which NIT devices perform better in conditions specific to Minnesota and provide cost estimations and maintenance recommendations for operating these devices year-round. The research had two main components: 1) synthesizing national and local experiences procuring, deploying, and maintaining NITs, and 2) evaluating real-world NIT deployments in Minnesota across different weather conditions. The team's results and analysis combined the results from these steps to make recommendations informed by research and real-world experience operating NIT devices.

Through interviews with Minnesota traffic signal operators, the research found that environmental factors like wind, snow, and rain cause most NIT failures, requiring costly on-site maintenance. Operators emphasized the need for central monitoring systems, sun shields, and heated lenses to maintain performance. The research then analyzed NIT video, signal actuation, and weather data at six Twin Cities intersections using Iteris and Autoscope Vision technologies. No single NIT performed best, aligning with previous findings, but Autoscope Vision was less prone to lens blockages requiring on-site service. The researchers' analysis also found some intersections have more failures, indicating location and geometry impact performance. Key recommendations are based on the relative performance of a NIT in different weather conditions and accounting for local weather conditions when selecting a NIT at an intersection. Researchers also recommend using central monitoring systems to troubleshoot remotely, installing heat shields to prevent snow/rain accumulation, and routine annual checks and checks after major storms.