LAYTON -- About one in every six people driving in the state's new express lane system is using it illegally.
Around 17 percent of the daily users of the express lane are violators, meaning they are single-occupancy vehicles traveling in the lane without a state-issued transponder, according to the Utah Department of Transportation.
Since the new system went into effect in August, UDOT has sold more than 8,700 transponders and has opened nearly 7,000 accounts.
UDOT officials are happy with the number of transponders purchased so far and hope to reach 10,000 by mid-2011, but spokeswoman Tonia Mashburn said the violation rate is higher than department officials would like to see.
"We have been seeing violators," she said, "but we are working on some things to hopefully get that number down."
UDOT recently installed a sign in the median near 5300 South in Salt Lake County that flashes yellow if a car passes through the express lane illegally.
UDOT hopes use of the sign, which could spread to other areas where express lanes exist, will work as a "community policing" measure to discourage violators.
"We hope that if other people can see when someone is in violation, that will help discourage it," Mashburn said. "A little peer pressure."
At several locations along the lanes, the state has already installed readers that detect in-vehicle Express Pass transponders as they travel through the zones. Drivers' accounts are charged when they exit.
The state uses the express lane payments to operate and maintain the system.
Utah Highway Patrol also has shifts dedicated to patrolling the lanes.
Mashburn said that, during congestion, vehicles in the express lane travel on average 10 mph faster than vehicles traveling in the general-purpose lanes.
"If you're using the lane illegally, you're just slowing down the lane for people who are carpooling or who have actually paid to use it," Mashburn said.
The express lane system runs from Main Street in Lehi to 2300 North in Salt Lake City and from Farmington's State Street to the south Layton interchange.
Electronic overhead signs show drivers the cost of entering the lane, and an online account is debited for each zone traveled through. The cost for driver-only use of the express lanes ranges from 25 cents to $1 per zone, depending on the level of traffic.
In December 2012, UDOT will extend the express lanes from Lehi to U.S. 6 in Spanish Fork.