Field Evaluations of an Adaptive Traffic Signal—Using Private-Sector Probe Data

This study evaluated the in-service performance of the InSync adaptive signal control (ASC) system utilizing field data collected from the private sector travel time vendor INRIX. A total of six corridors in Virginia were tested, with extensive data collected over 6 months. The measurements of effectiveness (MOEs) adopted are mainline delay savings and travel time reliability measurements (95th percentile travel time and buffer index). All the before-and-after MOEs were compared using t-tests, and the Pearson correlation of the MOEs with respect to various quantitative site-specific factors was assessed to determine if effectiveness could be tied to specific site characteristics. The results indicate that the adaptive signal control system generally reduces delay by about 25% and improves travel time reliability by about 16%. The performance of ASC system is affected by site-specific factors, like annual average daily traffic, signal density, and access point density.