When a driver runs a red light, the resulting right-angle crash can be dangerous or even deadly. Nearly 1,000 people were killed and more than 116,000 injured in red-light running crashes in the US in 2020. To help save lives, U of M researchers are working on effective countermeasures for red-light running violations in a project sponsored by the Minnesota Department of Transportation (MnDOT).
“Newer vehicles have many standard safety features such as lane-departure warning and brake-assistance systems to support drivers, yet they lack technologies to help prevent driving through red lights,” says Michael Levin, U of M associate professor of civil, environmental, and geo- engineering and a CTS scholar. “We wanted to create a system to warn drivers when they were approaching a red light to alert distracted drivers, decrease the rate of serious crashes, and improve road safety.”
Investigators began by installing a roadside unit at a signalized intersection in Scott County, Minnesota. Then, they equipped a car with a GPS chip that could receive location, speed, traffic signal phase, and signal timing information from the roadside unit.
“We knew that integrating our car’s location and speed with the timing of the traffic lights would be the foundation for operating the red-light warning system,” Levin says.
To accomplish this, the research team designed software to generate green, yellow, and red warning messages and then display the messages on a laptop screen in the car. As the driver approaches the intersection, the warning messages are presented as colored circles that give the driver important information: a green circle means the driver should drive normally, yellow means begin braking to avoid running a red light, and red means brake hard to avoid running a red light.
To test the design, the team started with computer simulations, then conducted on-road testing by driving the car through the intersection repeatedly to activate the red-light warning system and record the results.
The tests successfully demonstrated that the system could provide reliable warnings to prevent drivers from running red lights. For example, the system displayed yellow warnings when it was appropriate for the car to begin braking and red warnings when immediate, forceful braking was needed. In addition, as the car approached a green light that would turn red before it passed through the intersection, the system displayed a yellow warning—further demonstrating its ability to compute real-time warnings based on information from the roadside unit.
“Red-light running continues to be a major contributor to serious crashes at signalized intersections,” says St. Louis County Public Works traffic engineer Victor Lund. “The technology developed in this project has the potential to reduce the risk of these serious crashes through driver warnings.”
Besides preventing potential injuries and fatalities, a red-light warning system could generate significant cost savings. Researchers conducted a cost-benefit analysis, based on the cost to equip 650 signalized intersections in the Twin Cities metro area and 10 percent of the vehicles. They calculated a savings of more than $10 million—and 7,000 crashes—per year based on reductions in collisions, traffic citations, and road maintenance and improvements in traffic flow.
The researchers hope to continue developing this red-light warning system into a market-ready technology that better incorporates road conditions, weather, individual driver tendencies, and other factors. Additional plans include equipping multiple cars, driving vehicles through more intersections, and testing drivers with a range of driving behaviors.
—Megan Tsai, contributing writer
