Connected Traffic Signal Systems Reduce Congestion and Costs for Sonoma County Taxpayers

The county manages a network of roadways throughout the county and the county IT team provides support for traffic signals and intersections. 

Each of Sonoma County’s traffic intersections are “connected” via a SCADA system, and a typical intersection includes signals, pavement sensors and a controller typically located in close proximity to the system. The controller is connected to county operations, and enables the operations team to remotely monitor and control traffic flow across the region. When connected, these components can be outfitted with new software and traffic signal schedules which keep traffic flowing day and night. The average cost for an intersection is approximately $750,000. 

Until recently, each intersection was “hard-wired” to county’s operations using landlines. Each intersection is “always on”, and the system pings and polls each system regularly to get status. This wasn’t without its challenges, and proved increasingly unreliable with breakdowns every few days. In addition, when polls received information, the county’s operations team wasn’t notified, so a traffic signal could be out and the county would rely on law enforcement and the community to let them know. 

New timing could be downloaded to each intersection but, when failures occurred, all timing information was lost, resulting in manual re-loading of software on the controller. In addition, the cost of 24/7 operations was approximately $220,000 per year. Recently, the county’s carrier partner announced they would no longer provide the hardwire solution, forcing the county to look for alternate ways to keep intersections connected.

Also, much of the equipment in the traffic control system is 20 years old, which complicated finding a communications solution that would support legacy infrastructure.