During rush hour, northbound Yellow Line trains need to reverse direction at Mount Vernon Square because there isn’t enough capacity for all of them to run to Greenbelt. That’s because when Metro designed the Yellow Line, it was hard to imagine neighborhoods like Shaw and U Street developing as rapidly as they did.

This pre-2004 map shows original full-time Yellow Line service. Image from WMATA.

Why can’t Yellow Line go farther north full time full time?

For the Yellow Line to operate north of Mount Vernon Square full-time, there would need to be a pocket track somewhere between that station and Greenbelt, so that Yellow Line trains could turn back towards Virginia without impeding Green Line trains at rush hour. (Right now, a few Rush+ Yellow Line trains do go all the way to Greenbelt, but usually only about four per hour during peak periods).

The tunnel that carries the Green and Yellow Lines under 7th Street and U Street NW opened in two stages: from L’Enfant Plaza to Gallery Place in April 1983, and from Gallery Place to U Street in May 1991. These tracks initially only provided service for the Yellow Line, but the Green Line would soon utilize the tunnel when it began operation from U Street to Anacostia in December 1991. Check out the Evolution of Metrorail graphic below, which we initially ran two years ago to see how service has changed:

The tracks running through the 7th Street tunnel had always been intended to be shared by the Green and Yellow Lines, but only for a short portion. Although it was intended for the Green Line to operate along the entire length of the tunnel - continuing onwards to Petworth, Fort Totten, and northwest Prince George’s County - the Yellow Line would short turn at a pocket track somewhere along the route, so as not to overwhelm operations at Greenbelt (as I discussed in my first post on this topic).

Metro’s planners opted to build the necessary pocket track at Mount Vernon Square station, which meant that Yellow Line trains would have to end their route and turn back towards Virginia without serving neighborhoods like Columbia Heights and Petworth. Except for the brief six-month period between the opening of Mount Vernon Square, Shaw, and U Street stations in June 1991 and the commencement of Green Line service that December, the Yellow Line has always terminated at Mount Vernon Square in regular rush hour service.

Off-peak Yellow Line service all the way to Fort Totten began in 2006. This has certainly been a first step towards meeting the increased demand in DC’s Mid-City area (generally thought of as the neighborhoods served by the Green Line from Shaw to Petworth). However, these areas have now grown enough in population that full-time Yellow Line service is warranted, despite the significant obstacles that stand in the way.

The growth of Mid-City has led to a need for increased Metro service

Massive redevelopment in Mid-City began around the turn of the century, and has continued at a frantic pace to the present day. That’s meant increased demand for service along the Green/Yellow Lines at all hours.

When the Mid-City section of the Green Line opened in 1991 (between Gallery Place and U Street) and was completed in 1999 (from U Street to Fort Totten), the area was still reeling from the destruction caused by the 1968 riots. Shaw and Columbia Heights were still plagued with empty storefronts, and the landscape was pockmarked with empty lots where incinerated buildings had once stood.

Aftermath of DC’s 1968 riots. Image from the Library of Congress.

The corridor has since benefitted from an incredible amount of reinvestment since the opening of the new Green (later Green/Yellow) Line stations in the 1990s. New construction has ranged in scale from projects like Progression Place, a huge mixed-use center that was recently built directly atop Shaw Metro, to smaller infill developments aimed at repairing the urban fabric.

Apartments at the Columbia Heights station. Photo by Alice Crain on Flickr.

A problem inherent in the system’s design

Unfortunately, plans for Metro service patterns in Mid-City didn’t anticipate the future growth that these neighborhoods would face.  The Yellow Line was designed to provide a direct connection from Virginia to downtown for the commuting crowd; it travels express between Pentagon and L’Enfant Plaza, then provides a connection to each of the other Metro lines downtown before turning back at Mount Vernon Square.

The system’s planners didn’t predict that a significant amount of Yellow Line passengers would desire to travel past downtown, to neighborhoods like Shaw and Columbia Heights. Thus, it was assumed that the Green Line would provide adequate service for this portion of the line. Hence the pocket track going in at Mount Vernon Square, rather than at a more northern station like U Street.

So, could Metro build a new pocket track to account for the development spree?

Unfortunately, because this service pattern is cemented by the chosen location to build a pocket track, any attempt to correct this past oversight will be very laborious and costly.

It would be extremely difficult to add a pocket track to the Green and Yellow Lines anywhere between Mount Vernon Square and the District line because the tracks run almost entirely underground all the way to West Hyattsville. It would be prohibitively disruptive and expensive to excavate along the existing route and construct a pocket track between the mainline tracks — a WMATA study placed the cost of a Fort Totten pocket at $150 million.

Although the lower platform at Fort Totten is mostly built in an open cut (a shallow excavation that puts the tracks slightly below ground level), the tracks emerge directly from tunnels on both sides. The necessary location for a pocket track - the east side of the station, on the far side of the platforms from the city - is also the location of the B&E Connector track, a non-revenue link between the Red and Green Lines. The combination of these factors would make the construction of a pocket at this location very complex.

The track layout at Fort Totten. Light-colored tracks are below ground. Graphic by the author.

The next logical place to build a pocket track beyond Fort Totten is in Prince George’s County, at the point where the tracks emerge from underground near West Hyattsville station. However, while construction of a pocket here wouldn’t require excavation, it would still be extremely difficult and disruptive because the tracks are side-by-side on an elevated viaduct.

Because a pocket would have to be built between the existing mainline tracks, Metro would have to reconstruct a roughly 600-foot section of this elevated viaduct in order to pull the tracks apart and create space for a third track in between. This would be comparably disruptive and expensive to constructing a pocket track underground near Fort Totten. What’s really required is a section of track that is at-grade, e.g. resting at ground level rather than underground or on a viaduct.

The Green Line viaduct and platforms at West Hyattsville. Photo by Elvert Barnes on Flickr.

The next feasible place to build a pocket track would be at the above-ground embankment behind Home Depot on East-West Highway near Prince George’s Plaza station (although that, too, might be difficult due to the curve at that location).

Of course, a pocket track gets less and less useful the further it is from downtown. The next possible location for a pocket would be near College Park, at which point Yellow Line trains might as well continue all the way to Greenbelt.

It looks like for now, stations north of Mount Vernon Square will have to make do without full-time Yellow Line service. Until WMATA can procure $150 million to add an expensive new underground pocket track at Fort Totten, as well as $100 million for new rolling stock (plus millions more in annual operating funds), rush hour Yellow Line trains will have to continue to terminate at Mount Vernon Square. But the temporary terminus at U Street offers us a glimpse of what could have been if Metro had built a pocket track there back in 1991.