The evolution of infrastructure: 4-track subways and parking decks

With Rail~volution complete, several recaps of conference sessions have sparked some interesting discussion.  One panel posed the hypothetical question – what would DC look like today if we had never built Metro?

WMATA’s Nat Bottigheimer emphasized the linkage between high capacity rapid transit and the ability to support dense urban development, drawing a contrast to the spatial inefficiency of automobile-based systems:

Bottigheimer gave an analogue for Washington, DC, saying that the parking needed to serve all the cars that would come in place of Metro could fill the entire area from 12th to 23rd Streets, Constitution to R (including the White House) with 5-story parking decks.

That’s a lot pf parking.  It’s an absurd amount, really – but it shouldn’t be a surprise.  Consider an auto-oriented business district like Tysons Corner:

Tysons’ dependence on the automobile, and a place to park it, is dramatic when compared with other areas. With about 120,000 jobs, Tysons features nearly half again as many parking spots in structures, underground and in surface lots. That’s more parking, 40 million square feet, than office space, 28 million square feet. Tysons boasts more spaces, 167,000, than downtown Washington, 50,000, which has more than twice as many jobs.

Of course, downtown DC never would’ve developed in such a fashion.  Bottigheimer’s hypothetical is meant to draw a contrast rather than represent a plausible alternate universe.  Never the less, the ratio of space devoted to parking compared to space devoted to other stuff (offices, retail, housing, etc) is striking.  An auto-based transportation system requires the devotion of half of your space to just the terminal capacity for the car.

While acknowledging Metro’s power to shape development and growth when paired with appropriate land use and economic development policies, the GGW discussion turned (as it often does) to Metro’s constraints.  Several commenters ask – why not four tracks like New York?  Why not have express service?

Sample of Midtown Manhattan track maps from

New York’s four-track trunk lines are indeed impressive pieces of infrastructure, but it’s worth remembering that they are essentially the second system of rapid transit in the city.  New York did not build those four-track lines from scratch, they built them to replace an extensive network of elevated trains. Consider the changes from 1904 (left), to 1932 (center), to present (right):

Red lines are elevateds, blue lines are subways – source images from Wikipedia. The process of replacing older elevated trains with subways is clear, particularly in Manhattan and around Downtown Brooklyn. The relevance to DC is that four-track subway lines don’t just happen.  The circumstances in New York that desired to get rid of most of the elevated tracks provided an opportunity to rebuild all of New York’s transit infrastructure.  Metro is not provided with such an opportunity.  Adding express tracks to the existing system would require essentially rebuilding the entire system, and without a compelling reason to do so (such as New York’s removal of Els), it’s simply not going to happen – no matter if it were a good idea and a cost-effective idea or not.

Perhaps the single biggest opportunity for an express level of service would be the conversion of MARC and VRE into a through-running S-Bahn-like transit service. Portions of the Red Line do indeed have four tracks – its just that two of them are for freight and commuter rail.  Likewise, should there be future expansion of Metro within the core (such as a separated Blue line) there would be the opportunity to study making such a tunnel a four-track line.  That concept would have to include a number of different ideas, however – future expansions to link into that capacity, surface/subway hybrid service for streetcar (such as in Philadelphia or San Francisco), etc.

5 comments to The evolution of infrastructure: 4-track subways and parking decks

  • You’re right that the easiest way to get express service is through the rail lines, but express service has to get to Tysons somehow, and provide service to northern Fairfax.

    That will almost certainly require new tunneling.

  • Alex Block


    One idea for express to Tysons would be to only have a new silver line tunnel from Ballston to Rosslyn (where it could connect to perhaps a new 4-track Blue line) – then you could fairly easily add 2 extra tracks to the current Orange line in I-66 between Ballston and WFC. You could also build a Tysons bypass by keeping the Silver line along the Toll Road, and that combination of infrastructure could offer substantially reduced times from Reston/Dulles into the core.


    In general, I’d agree – particularly with the operational issues to increase the span of service. I would love 24/7 operation.

    I could see a few cases where 4-tracking would be useful, however. The real question would be if it could justify the cost.

  • On the other hand, a fairly convincing case may be presented that the Orange/Silver interline between Rosslyn and East Falls Church, particularly if there are no long-term plans to separate them out. If, on the other hand, the Orange (or Silver) line were diverted, say north to Langley, then the need for full express tracks would obviously be curtailed.

    The triple interlining seems like it demands express tracks. However, I think it is much better to run a new tunnel for one of these lines. The Blue or Silver Line through Georgetown, for example. A rough sketch of my idea can be found here; sooner or later, I’ll have to take new input and refine it.

  • Alex Block

    Steve, good points.

    Really, despite being branded as its own line, the Silver line will be a long branch of the Orange line when all is said and done. Branching divides frequency, but since we’re talking about long segments of track in urbanizing but not truly walkable areas, that division of service should be OK for now.

    I’d clarify your second comment to note that the current and future arrangement of three services sharing one tunnel in downtown DC demands more capacity, not necessarily more capacity via express tracks. I think a new blue line for E-W crosstown travel would be a wise investment, as it removes some of the branching and therefore allows greatly increased frequency on current portions of the Orange and Blue lines that now share track.

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