LEHI — Think Main Street is crowded now? Wait until a new commuter train begins operations in three to five years.

Mayor Howard Johnson is warning that FrontRunner could shut down traffic on the narrow, busy street at its only roundabout up to 100 times a day. The railroad tracks where an estimated 75 commuter trains and 25 freight and Amtrak trains would run daily are less than a block from the roundabout.

Johnson wants the state to help build an underpass to keep motorists moving. Some 22,000 vehicles travel the two-lane street every day, he said.

His calculations show that Main Street could be closed a combined three hours every day as the trains go by. Main Street is a state road, which means "we can't even paint the curbs red without permission," he said.

The Utah Department of Transportation hasn't allocated any money for an underpass, spokesman Adan Carrillo said. He estimated an underpass to cost $23 million. The state will continue to work with Lehi officials and the Utah Transit Authority to come up with a solution, he said.

It would take three years to get an underpass on the state transportation list and five years to begin allocating money for it, Johnson said. He is approaching the Mountainland Association of Governments and the county "to get a few million (dollars)," he said.

The mayor is also looking at UTA and Union Pacific to kick in $3 million. "We can dig up $7.6 million," Johnson said.

But that still leaves a huge shortfall.

"If (an underpass) is not built, we're going to have one mess for the rest of our history," he said.

UTA is planning to push its FrontRunner commuter train south after launching the line north of Salt Lake City earlier this year. It broke ground on the southern line recently near Thanksgiving Point, where a passenger station is planned.

The line was originally in the Wasatch Front Regional Council's 2030 plan, but Utah County voters increased their sales tax in 2006 to speed up rail service in their area.

A planned 44-mile line, it is to have stops in Salt Lake City, Murray, Sandy/South Jordan, Draper/Bluffdale, Lehi, American Fork, Orem and Provo. FrontRunner South is part of the Front Lines 2015 project, but it could be finished by 2010 or 2013, Johnson said.