Evaluation of Traffic Signal Communication

The Arizona Department of Transportation's traffic signal systems are maintained and operated by Regional Traffic Engineering (RTE) groups. Each RTE group oversees 150 to 200 traffic signals across a large geographic area. The Southern RTE group recently installed three separate systems that provide real-time data enabling traffic signal failure alerts, video monitoring, and remote controller programming. These systems are located on State Route 347 in Maricopa, Arizona; State Route189 in Nogales, Arizona; and State Route 77 in Tucson. The capability of the new systems allows for reduced response time to address signal outages, for more informed decisions regarding signal repair, and for timing adjustments to overcome malfunctioning signals or to improve traffic flow. Signal timing adjustments can be done manually or automatically by the system, also called adaptive signal control (ASC). However, the three systems vary significantly in the type and scope of technology installed. The SR 189 system, the most advanced, includes significant detection capabilities and ASC. Comparison of these systems is needed to determine standard configurations for deployment on additional state highways.