 The route leaves I-70 at exit 244, to the east of Idaho Springs and rejoins it again at between exits 252 and 254 in El Rancho.It parallels I-70, mostly as a frontage road, until the intersection with former State Highway 26 (SH 26) to the south of Golden

Beginning in Golden, US 40 becomes Colfax Avenue, the main east–west thoroughfare through the Denver-Aurora Metropolitan Area.Along with US 40, the entire route along Colfax Avenue is cosigned as Business Loop 70.