Making SMART Signal even smarter

intersection
Photo: Shannon Fiecke, MnDOT

Your drive home may be a few minutes quicker thanks to a team of researchers who are making it easier for Minnesota engineers to retime traffic signals.

Traffic delays typically grow 3 to 5 percent per year due to outdated signal timing. However, most traffic signals in the United States are only retimed every two to five years (or longer), largely due to the expense associated with retiming efforts. It normally costs $3,500 to retime one traffic signal because of the time involved in collecting data and optimizing timings.

But over the past several years, University of Minnesota researchers have developed and refined the SMART Signal system to make it easier and less expensive to retime signals. The system—developed with funding from the Minnesota Department of Transportation (MnDOT)—not only collects traffic and signal-phase data automatically, but it also identifies under-performing traffic signals and generates optimal signal timing plans with minimal human intervention.

MnDOT (along with many cities and counties) embeds loop detectors in roads that notify a traffic signal when a vehicle is present. Staff normally must manually track wait times to determine how signal timing is affecting traffic.

But SMART Signal automates much of this process by recording how long a vehicle waits at an intersection and automatically reporting the data (along with signal timing) to a central server. The data—viewable in real-time on a website—can then be analyzed to determine traffic patterns and optimal signal timing. By reducing the cost of data collection and performance measurement, SMART Signal allows MnDOT to base signal retiming decisions on performance rather than a fixed schedule.

The latest research optimizes the system’s ability to reduce traffic delays by developing a framework to diagnose problems that cause delays at traffic signals and an algorithm that automatically optimizes the signal plan to address these problems.

The enhancements were successfully tested on Highway 13 in Burnsville, reducing vehicle delay there by 5 percent. The benefit could be in the double digits for corridors with worse traffic delays.

The software upgrade has since been integrated into the more than 100 intersections in Minnesota equipped with the SMART Signal system.

(Adapted from an article published on the joint CTS/MnDOT Crossroads blog.)

More Information

Subscribe

Sign up to receive our Catalyst newsletter in your inbox twice every month.

Media Contact

Michael McCarthy
612-624-3645