Utah Department of Transportation crews have begun re-striping 38 miles of carpool lanes on I-15, turning them into "express" lanes.

The express lanes — also known as HOT lanes, or "high-occupancy toll" lanes — will be available for use by individual drivers who are willing to pay a fee to use the lanes. Buses, motorcycles, environmentally friendly vehicles and car poolers can still use the lanes free.

Work to convert the I-15 carpool lanes into express lanes began Monday night at 600 North in Salt Lake City. Crews will be re-striping the southbound lanes, a half-mile stretch at a time, until they reach the Salt Lake/Utah County line. Then they will turn around and work on the northbound side of I-15.

That process is expected to take until mid-August and the express lanes are scheduled to open Sept. 1. All of the work will take place between the hours of 9 p.m. and 6 a.m. on Monday through Thursday nights. Some work also will take place on Friday nights.

UDOT crews in Utah County will be re-striping lanes there. That portion of the project has not yet begun, said UDOT representative Bethany Eller. Twenty-six miles of the carpool/express lanes are located in Salt Lake County. The other 12 are in Utah County.

In April, the Utah Transportation Commission gave UDOT permission to install express lanes from 600 North to University Parkway in Orem.