As Northern Utah’s population continues skyward with no sign of slowing, space on the road is at a premium now more than ever.

And as the Utah Department of Transportation continues to add to its Express Lanes system, hoping to make better use of available real estate, it’s studying how to stop motorists from using the system illegally.

During their 2018 general session, the Utah Legislature passed Senate Bill 71, which allows the transportation department to use cameras, license plate readers and other technology to catch and penalize Express Lane cheaters.

But UDOT Director of Traffic Management Troy Peterson said the camera technology is proving to be expensive.

“This technology has been around for about 10 years,” Peterson said. “But it comes with a pretty high implementation or deployment cost, as well as a high (cost) of annual maintenance for it.”

So the state has procured a trial of a cellphone app to help validate vehicle occupancy among cars that travel through the lanes. Peterson said UDOT’s Traffic Management Division will engage up to 500 participants in a study to evaluate acceptance and ease of use of the app, its accuracy, and the ability of drivers to cheat the system.

Peterson said for six months, the 500 participants will have Express Lanes fees waived and will be required to make eight carpool trips in the Express Lanes each month.

The state’s Express Lane system is made of seven segments from Spanish Fork to Layton and allows carpoolers, buses, motorcycles and emergency vehicles to use a dedicated lane on the left side of I-15. Solo drivers can drive in the lane for a fee if space is available. UDOT collects those fees through an electronic payment system that charges drivers based on an algorithm that adjusts prices based on current traffic conditions — the thicker the traffic, the larger the fee.

Success of the system hinges on traffic flowing smoothly in the dedicated lane, despite congestion outside of it. But recently, traffic flow has been deteriorating at the busiest points of the system, mostly during evening commutes. The topic has been discussed at multiple transportation commission meetings over the past few years.

Part of the problem is the high rate of solo motorists illegally using the system. Violators can be fined $337 and see the infraction go on their driving record, but right now the Utah Highway Patrol serves as the system’s only enforcement mechanism.

As part of a $169 million project, UDOT is currently adding Express Lanes to north and southbound I-15 between Hill Field Road in Layton and Interstate 84 near the Riverdale/Ogden border.

The project isn’t scheduled to be complete until 2021. Once it’s done, Utah’s Express Lanes system will extend 80 miles, running continuously from Utah County to Weber County. UDOT officials have said the completed project will make Utah’s Express Lane the longest uninterrupted system in the United States.