The Interstate 25 project in Colorado included adding a managed lane on the inside shoulder in each direction along six miles along the interchange. This new lane connects to the existing Interstate 25 Express Lanes to and from downtown Denver. Flatiron resurfaced the existing lanes along this six-mile stretch.

Flatiron is constructed this project along an especially congested section north of Denver where interstates 25, 70, 270, and US 36 (to Boulder) intersect, with traffic volumes upwards of 140,000 vehicles per day. The new express lanes tie in to existing tolled lanes that carry traffic south to downtown Denver. Buses and carpools will be able to use the new lane free of charge, while solo drivers will be required to pay a toll. The route provides a continuous managed lane alternate for commuters, greatly reducing commute times.

In addition, the lowering of Interstate 25 profile at the 88th Avenue Bridge improves vertical clearance under the existing overpass. The project also included reconstructing the outside shoulders, repaving and restriping the existing lanes, complete drainage improvements, install water quality facilities, installing tolling infrastructure and constructing noise walls.

Construction-wise, the work has three distinct scopes. One phase was a shoulder reconstruction to bring the shoulder pavement up to interstate standards. Another was the installation of new overhead signs with tolling devices and Intelligent Transportation Systems, and the final phase was asphalt overlay across the full pavement width.