Metro FAQ: Why doesn’t Metro have four-track routes?
25 April 2016
Ten years ago, when Metro was still working well enough for people to wish for more, the more frequent question I got was about the lack of a Metro station in Georgetown. Now that the challenge is to keep the current system functioning, the question is why Metro has only two sets of tracks on each route, so that shutting one down for repairs causes slow service.
In my research, I found two documents that explained the decision particularly well.
The key points are:
1. Yes, planners did consider the four-track option.
2. In doing so, they were concerned about the trade-off between speed and cost. I don’t think any professionals in Washington or any other city considered building long stretches of spare tracks just to allow maintenance, the way extra escalators were built. The costs are simply too great.
3. Metro does not lack fast routes, since the wide spacing of stations in the suburbs make them the equivalent of express lines elsewhere. Rather, Metro lacks the slow, hyper-local routes like the Broadway Local in New York City, which stops every few blocks to serve the tens of thousands people in apartment buildings.
4. Given finite funds, building four-track routes in one place would have meant cutting routes elsewhere. Planners opted instead to build more two-track routes. In the busiest stretch of the system, from Farragut Square to Capitol Hill, this resulted in four tracks: two Red, two Orange/Blue.
Today’s Washington Post story, “Metro Sank into Crisis despite Decades of Warnings,” also mentions pocket tracks. To be clear, Metro does have some pocket tracks, but I’m afraid I don’t have documents explaining who decided where these should go.
U.S. National Capital Transportation Agency, Appendix to November 1, 1962 Report to the President. Volume V: System Planning (1963), 112.
In the District, alternative routes (along Georgia Avenue, for example) running from downtown to join the B&O near Silver Spring required costly subways under the street, open cut construction through residential property, or aerial structure.
Those alternatives, as well as an alternative that would carry Rockville area passengers through Northwest Washington, had a problem in common: the need to operate rapid transit for two different kinds of development—(1) densely built-up areas with frequent station stops, and lower speeds, in and near the District, and (2) a long suburban corridor with widely spaced stations. Other cities have solved this problem by providing (1) express and local service on four-track rapid transit routes or (2) shorter urban routes with numerous stations in the densely developed close-in area and high-speed suburban routes in a separate location to serve more distant areas. NCTA has adopted the latter solution. The densely settled Columbia Heights-Petworth areas are served by a short branch line from the Northwest Route; express service is provided by the B&O route. The Petworth route can later be extended.
Jackson Graham to Congressman Gilbert Gude, 4 February 1974, Gilbert Gude Papers, George Washington University, box 95, folder: WMATA.
We have reviewed with interest Mr. Ralph G. Golden’s letter of November 3, 1973, with regard to the addition of a third track to the various routes of our rapid transit system. Multiple track rapid transit routes can be justified only by the existence of huge passenger volumes. Consequently, this type of operation is found extensively only in New York City and one line each in Chicago and Philadelphia. An operation of this type would not be feasible economically in the Washington metropolitan area.
The lack of a third track is not as serious as Mr. Golden suggests. With regard to passenger capacity, each one of our lines has a capacity, based on a 90-second headway with eight car trains, of 56,000 passengers per hour in each direction past the peak point. This capacity is far in excess of the potential loads for any of our lines as estimated by our Office of Planning.
With regard to express trains, the average speed of the Washington Metro will be approximately 35 mph. This is as high as the average speeds of express trains in either New York or Chicago. If higher speeds are required in the future, our Automatic Train Control System will permit the use of a skip stop system whereby alternate trains pass alternate stations. Such a system which permits the establishment of an express-type service on a two-track rapid transit line has been successfully used in Chicago, Philadelphia, Boston and even in New York.
Mr. Golden was mistaken in his statement ‘If an accident occurs all traffic will be stopped.’ First of all, because the failure of an individual car does not stop a rapid transit train, there are only a limited number of delays on a rapid transit system. When a serious delay does occur, we will bypass the blockage by operating in reverse direction on the opposite track. Our system has been designed so that a minimum headway of ten minutes can be maintained in each direction when operating in both directions on a single track.
In view of all of this, we feel that any additional monies that might be made available for rapid transit should be invested in extension of our system rather than providing surplus capacity in the form of a third track.