History
When it opened in 2002, C Line trains operated seven days a week but ran to Littleton–Mineral station only during peak hours and sporting events. At all other times, C Line service operated to between Union Station and I-25 & Broadway, with service to Littleton via the D Line. C Line trains would begin operating the full length of the line in 2003.
When the Southeast Corridor was opened in 2006, weekend C Line service was discontinued except for certain sporting events. Capacity between 10th & Osage station and Union Station was replaced by the E Line.
In 2009, the mid-day service pattern between Union Station and I-25/Broadway was resumed and evening service discontinued. Midday weekday service was discontinued in 2012 and was reinstated in 2014. When suspended, the route was served by the D and E Lines, with a transfer at I-25 & Broadway.
Suspension from service (2021-2026)
RTD suspended the C Line as a result of the COVID-19 pandemic in its January 2021 service change. The line was officially eliminated in RTD's January 2023 service change. However, due to the Downtown Rail Reconstruction Project, the D Line's northern terminus was diverted to Union Station in the summers of 2024 and 2025, following the route of the C Line but retaining the D Line designation. In June 2026, the D Line was instead suspended - rather than diverted - following resumption of construction. As a result, the C Line designation was temporarily revived for trains using the Southwest Corridor to Union Station. This temporary service pattern became permanent in RTD's September 2026 service change, restoring the C Line and eliminating the D Line from service.
Planned extension to Highlands Ranch
FasTracks provisions for a new southern terminus at C-470 and Kendrick Castillo Way in Highlands Ranch. This extension will add 2.5 mi (4.02 km) to the C Line, and feature a 1,000-space park-and-ride garage. An environmental evaluation for the station was completed in 2010. Plans for the design of this station were made along with the environmental evaluation; however, the project has not received funding and there is no timeline for the station's construction. Additionally, the 2010 evaluation suggested an intermediate station at C-470 and South Erickson Boulevard, which was not a part of the original FasTracks plan.
FasTracks also provisions for the addition of an infill station at West Bates Avenue in Englewood. No progress on the station has been made since FasTracks' approval in 2004 and as with the Highlands Ranch extension, there is no timeline for the construction of the station.
