The new toll system for express lanes on U.S. 36 between Denver and Boulder begins Wednesday. And the state transportation department really wants drivers who use the highway to get a tolling transponder.

This gizmos attach to a car’s windshield, just below the rearview mirror. Drivers without a transponder will pay a higher toll to use the lanes.

Depending on the number of passengers in the vehicle, the device can be switched to HOV mode for toll free travel. The express lanes run from Federal Boulevard in Denver to 88th Street in Louisville. They'll eventually continue onto Boulder. Toll rates in the lanes will change depending on the time of day.