B Line


  • Length (miles): 5.7 miles (41 miles future total)
  • Vehicle Type: Diesel commuter rail (Westminster segment: electric)
  • Stations: 10 (currently 4: Westminster Station, Pecos Junction, 41st & Fox, and Union Station)
  • Parking: 1,150 spaces
  • Service Frequency: 30 min (peak) / 60 min (off-peak)

At a Glance

  • The B Line, also referred to as the Northwest Rail Line, is part of RTD’s 2004 voter-approved FasTracks plan to expand transit across the Denver metro region.
  • The proposed 41-mile diesel commuter rail corridor would operate between Denver’s Union Station and Longmont, passing through north Denver, Adams County, Westminster, Broomfield, Louisville, Boulder, and Boulder County.
  • The line's seven proposed stations are Westminster (completed July 25, 2016), Church Ranch, Flatiron, Louisville, Boulder Transit Village, Gunbarrel, and downtown Longmont.

Project Overview

  • 2010: RTD FasTracks Environmental Evaluation was completed, identifying the benefits and effects of implementing transit on BNSF Railway right-of-way.
  • 2012: Construction of the first 6.2-mile electrified segment between Union and Westminster stations began as part of the Eagle P3 project set to open in 2016.
  • 2013-2014: RTD and its contractor completed the Northwest Area Mobility Study to determine the best mobility options for northwest communities including, the feasibility of building the Northwest Rail in phases and providing arterial bus rapid transit.
  • 2015-2016: RTD FasTracks earmarked $17 million to build the first phase of the end-of-line station in Longmont under a construction-ready plan; RTD will use the station for bus transfers then upgrade to a rail/bus facility after it completes the B Line Rail. Construction of the station will begin in 2015 and end in 2016.
  • 2016: The first B Line segment opened on July 25. RTD will begin additional construction when funding becomes available.


  • 2019 Total Ridership: 477,286