The Boulder-Denver Turnpike (U.S. 36) opened to traffic in 1952 as a four-lane toll road. Tolling ceased in 1968 shortly after the facility's underlying toll revenue bonds were repaid. Originally built with just one interchange along its 18.2-mile length, it now has 10 access points and became increasingly congested due to rapid population growth in the region.
Planning and environmental studies conducted by Colorado Department of Transportation (CDOT) in the late 1990s and 2000s explored options for expanding capacity on U.S. 36. A Major Investment Study (MIS) was conducted from 1998 to 2001 to consider improvements to the facility and multimodal solutions to relieve congestion. Environmental assessment began in 2003 to analyze the impacts of several alternatives, including one that would add commuter rail to the freight rail corridor parallel to U.S. 36. The commuter rail plan was ultimately abandoned in 2006 when voters in the region approved the FasTrack program, which would support a number of transit improvements in the metropolitan area.
Following the release of the draft environmental document in 2007 and several rounds of public and stakeholder input, the preferred alternative included two new managed lanes in the corridor, BRT system improvements, extensive bridge repair or replacement, and auxiliary lane additions between most interchanges. The project advanced into the final environmental review stage and gained approval from the Federal Highway Administration (FHWA) and Federal Transit Administration (FTA) in December 2009.