Frustrated by a parts shortage that has kept more than 1,100 drivers waiting months to get MnPass transponders, the Minnesota Department of Transportation (MnDOT) is moving on.

The agency said Wednesday that it's seeking new vendors for the devices that deduct tolls from solo drivers who drive in High Occupancy Toll (HOT) lanes.

The move comes as MnDOT's contract with the Israeli manufacturer of the current transponders expires and the agency begins taking steps to make Mn Pass compatible with tolling systems in other states.

One vendor, or more, could be selected as soon as the end of the month, said MnDOT spokesman Brian Kary. But it could take as long as two years before MnPass transponder holders could use them in other states, or that holders of devices elsewhere could use them in Minnesota.

"We are getting set up to accept different readers," Kary said. "We are getting the hardware side ready."

MnDOT is required to make its system compatible with other states by 2016, due to a mandate from the Federal Highway Administration. The agency got the ball rolling earlier this year when it was unable to get clips from its lone vendor, Telematics Wireless. The clips are a key part of the transponders that allow readers along the HOT lanes on I-394 and I-35W to deduct tolls electronically.

The shortage forced the agency in February to delay enrolling more drivers. The current waiting list is more than 1,165, MnDOT said. About 500 people a month sign up.

"That was upsetting to us," Kary said. "They told us at the last minute."

Drivers who initially were told they could sign up in April are being told that new transponders won't arrive until late June or early July.

"People are anxious to get them because of the construction delays on Hwy. 12 in the area of I-494," said MnDOT spokeswoman Bobbie Dahlke. "People coming in from the way west want to bypass the congestion around the 494/394 area and want to use the MnPass lane and can't."

By seeking multiple vendors, the agency is unlikely to face a repeat of the clip problem, Dahlke said.

There are currently about 25,000 customers with transponders, and that number likely to rise with the opening of the new HOT lane later this year on I-35E through St. Paul and Maplewood.