• Length (miles): 41
  • Vehicle Type: electric commuter rail to Westminster Station
  • Vehicle Type: diesel commuter rail in future development
  • Stations: 7
  • Parking: 4,393 new 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; it will operate as the B Line upon completion.
  • 2013-2014: RTD FasTracks and its contractor completed the 15-month-long 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: Westminster Station opened for service to Denver Union Station on July 25.
  • Future: RTD FasTracks will begin construction on the line between Westminster and Longmont when funding becomes available.




  • Annual boardings: 571,317


Updated August 2019