[2] Part of the FasTracks project, the first 6.2-mile (10 km) section from downtown Denver to south Westminster opened on July 25, 2016.

It runs on a railroad right-of-way north sharing track with the G Line until Pecos Junction station, after which the two routes diverge.

The remaining segment, extending to downtown Longmont, will require additional funding[7] in order to be completed prior to 2042.

[4] The announcement angered many voters in the cities and suburbs north of Denver, who had approved a sales tax increase in 2004 to fund the FasTracks project.

[10][11][12][13][14] In summer 2018, the U.S. 36 Mayors and Commissioners Coalition was gathering support from other members to ask RTD to provide an estimate for at least weekday rush hour commuter rail service along the original corridor to Longmont.