Park City's 'Smart' Traffic Signals Became 'Dumb' Ones, Causing Traffic Jam

Feb 28, 2019

Park City commuters experienced bumper-to-bumper traffic during their drives home Tuesday, due to a drop in communication between traffic signals and the Utah Department of Transportation. 

Traffic on S.R. 224 was backed up for several miles in the 5 p.m. hour Tuesday, after UDOT lost connection with the adaptive traffic signals in Park City. The signals trigger the red, yellow and green traffic lights at intersections to adjust for traffic demand, so that when there’s more traffic going one way at an intersection, signal timing is adjusted to accommodate more cars. Park City Transportation Planning Manager Alfred Knotts says when UDOT lost connection to the adaptive signals, the traffic signals went back to giving each light an equal amount of run time.

“Say you’re at Snow Creek, and you’re trying to go northbound, and there’s one car at Snow Creek," Knotts said. "It gives equal priority to all movements, but when the adaptive system is in place, it would typically give that movement about 10 seconds, versus giving the other movement up to 210 seconds.”

Basically, Knotts says, “They’re smart signals that turned into dumb signals.”

To Knotts’ knowledge, the backup didn’t result in any accidents, but he says when congestion like that happens, a concern for public safety arises because it’s more difficult for emergency vehicles to maneuver through traffic in response to incidents.

Knotts says a drop in UDOT’s server caused the issue, akin to the Internet going down. He says UDOT informed him signals were back up at about 8:30 p.m., and the problem highlighted Park City’s reliance on technology for a smooth transportation experience.

“A lot of people don’t know on a day-to-day basis how effective those signals are, and when they do go down, I think now everybody can see just how critical the technology is to our overall system.”

Knotts says during the recent peak event season, the city managed the adaptive signals based on traffic surrounding the events. UDOT manages them on a day-to-day basis.