Galleries | Metro | Streetcars | U.S. Capitol | Heavy Rail

The Unites States Capitol Subway System

Follow BelowTheCapital on Twitter
Maglite The Urban Exploration Ring [ Join Now | Ring Hub | Random | <<Prev | Next>> ]

If you have information that you would like to share, please contact carguy at carguy at Thank you!


The Capitol subway consists of three lines: two on the Senate side on the north side of the Capitol, and one on the House side on the south side of the Capitol. The dotted lines on the upper map show the two lines from the Senate side of the Capitol to the three Senate Office Buildings. The House has only one line from the House side to the Rayburn House Office Building (The dotted line from the Capitol to the Cannon House Office Building is a pedestrian walkway only). See the lower map for a more detailed view of the area.

Senate side:

Image from Force Engineering

Two subway lines serve three Senate Office Buildings and have a long history. Starting in 1909, the Senate Office Buildings were serviced by an electric bus. This was replaced in 1912 by a monorail vehicle which featured a wicker coach. This monorail, I have been told, can be seen in the movie "Advise and Consent." In 1960, this monorail was replaced by trolleys, one of which remains today and runs between the Senate side and the Russell Senate Office Building. At this time, the tunnels were apparently enlarged to accommodate the new trolleys.

The trolleys installed in 1960 still run on the shortest line that runs from the Senate side to the Russell Senate Office Building. There are two trains and each runs on a dedicated track (i.e., no switches or crossovers). They are manually operated by conductors and are powered by a catenary wire. The cars themselves are open with no sides or roof. The electrical tower that leads to the catenary wires are simple aluminum duct work - very ugly. Because of the overhead lines and the manual conductor, the tracks are not separated from the adjacent pedestrian walkway by any significant barriers. These two tracks run on the north side of the tunnel.

Along the south side of the same tunnel that serves the Russell Senate Office Building, a new subway serving the remaining two buildings, Dirksen and Hart, runs parallel until the tunnel splits shortly before Russell. A pedestrian walkway runs down the middle of the tunnel until the split. The subway to Dirksen and Hart was installed in 1993, replacing the system installed in 1960. Marks along the roof of the tunnel show where the catenary wire ran.

The new trains are fully enclosed with a mesh roof and each train consists of three cars - one of which appears to be reserved for senators. Because of the power system, described below, the tracks are isolated from the walkway by a waist-high balustrade with plexiglass barriers mounted on top. At the stations, the tracks are isolated from the platform by automatic doors that synch with the train car doors. Multiple cars run along these tracks so there are Y terminals at each end of the line at Hart and the Senate side and a center platform at Dirksen.

The new cars are fully automated and driverless and operate using an Automatic Vehicle Operation (AVO) control system and a Supervisory Control and Data Acquisition (SCADA) System provided by Transdyn Controls. The AVO system consists of six motor control centers. Each motor control center houses a Programmable Logic Controller (PLC) communicating over serial links to Variable Frequency Drives (VFDs). The VFDs control a series of linear induction motors that apply thrust to the vehicles. Each trolley is a passive unit; and braking, vehicle detection, and speed control are all handled by the wayside units housing the AVO. The control system is also responsible for station docking, door control, switch control, and interaction with the Automatic Vehicle Protection System as well as monitoring system power and all aspects of the vehicle such as daily schedules, operating modes, and vehicle headways. This AVO system runs across a fiber-optic backbone.

Motion is provided by 506 linear induction motors (LIMs) lining the tracks at intervals of 4.5 to 9 feet (1.5 to 3 meters). Steel-backed aluminum reaction plates are mounted underneath the passive cars. The LIMs were built by Force Engineering and are also contained in the wayside units. Vehicle sensors and control equipment are fitted in each LIM junction box. All LIMs are connected to the same inverter driven bus bar system. As the vehicles accelerate and brake, the frequency and voltage fed to the bus is varied by the main computer to regulate performance.

The route itself is a double track loop of 3,100 feet (945 meters) and the cars normally operate in "pinched loop" mode with four (4) vehicles in operation at any given time with sixty-second headways. The vehicles can also operate in "shuttle" mode allowing one (1) car to shuttle back and forth on a single track. Each train weighs about 9,000 pounds (4,100 kg.) with a passenger capacity of up to 7,000 pounds (2,700 kg.) and runs at speeds up to 14 mph. Engineering services for the 1993 installation were provided by Lea+Elliott.

One of two monorail cars that ran from 1915 to 1961 on the original Senate subway line.

The monorail cars were built at the Washington Navy Yard in 1915 and 1920. The cars seated 18 passengers. Operations ceased on Sept. 28, 1961.

Close-up of monorail and the traction / drive mechanism.

Modern operatorless subway car traveling the system that runs from the senate side to Dirksen and Hart SOBs.

View of midpoint station at Dirksen SOB.

View of tracks on the modern system. Note LIMs between the tracks and waypoint AVO hardware.

View of tunnel looking toward the senate side and the split. Tracks on left run to Dirksen and Hart. Note subway car approaching. Tracks on right are part of the 1960 system that runs to Russell. Note the catenary wires on the Russell SOB line.

Industry photo of modern subway car that runs to Dirksen and Hart.

1960s era subway car that runs to Russell SOB undergoing maintenance. Notes catenary mounted to the roof. Ductwork that usually connects the subway car to the catenary has been removed to facilitate maintenance.

House side:

View of one of the two House subways stations. I'm recollecting that this is the House side, but I can't be sure (pictures were taken a while ago).

Similar view of the House station.

View of tracks from the House station. Note the subway car being repaired. I'm guessing this is the House side based on the track grade.

View down the tracks from the other station, the Rayburn side, if I am correct. Tracks rise up the hill toward the House side.

View down the tracks from the first station..

View of the maintenance pit from the same position.

Subway car has been elevated (note hydraulic lifts under car) for maintenance.

Same view. Note catenary track has been removed to lift vehicle.

Close-up of undercarriage.

Close-up of catenary system.

Close-up of vehicle controls.

Maps courtesy of the United States Senate and the United States House of Representatives.

Return Home to

© 1999, 2000, 2001, 2002, 2008 carguy All Rights Reserved