I’ve been thinking intermittently about how to relieve the capacity crunch on the Washington Metro. The worst peak crowding is on the Orange Line heading eastbound from Arlington to Downtown Washington, and this led to proposals to build a parallel tunnel for the Blue Line. Already a year ago, I had an alternative proposal, borrowing liberally from the ideas of alert reader Devin Bunten, who proposed a separate Yellow Line tunnel instead. Matt Yglesias’s last post about it, using my ideas, made this a bigger topic of discussion, and I’d like to explain my reasoning here.
Here is the map of what I think Metro needs to do:
Existing stations have gray fill, new ones have white fill. The Yellow Line gets its own route to Union Station, either parallel to the Orange Line and then north via the Capitol (which is easier to build) or parallel to the Green Line (which passes closer to the CBD), and then takes over the route to Glenmont. The rump Red Line then gets a tunnel under H Street, hosting the busiest bus in the city, and then takes over the current Blue Line to Largo, with an infill station in Mayfair for a transfer to the Orange Line and another at Minnesota Avenue for bus connections.
The Blue Line no longer presents a reverse-branch. It is reduced to a shuttle between the Pentagon and Rosslyn. Matt mistakenly claims that reducing the Blue Line to a shuttle is cost-free; in fact, it would need dedicated tracks at Rosslyn (if only a single track, based on projected frequency), an expensive retrofit that has also been discussed as part of the separate Blue Line tunnel project. At the Pentagon, initially shared tracks would be okay, since the Yellow Line is still a branch combined with the Green Line today; but the separate Yellow Line tracks would then force dedicated turnback tracks for the Blue Line at the Pentagon as well. Frequency should be high all day, and at times of low frequency (worse than about a train every 6 minutes), the lines in Virginia should be scheduled to permit fast transfers between both the Yellow and Orange Lines and the Blue Line.
The reverse branch today limits train frequency at the peak, because delays on one line propagate to the others. Peak capacity on Metro today is 26 trains per hour. I don’t know of anywhere with reverse-branching and much higher capacity: the London Underground lines that reverse-branch, such as the Northern line, have similar peak traffic, whereas ones that only conventionally branch (Central) or don’t branch at all (Victoria) are capable of 35-36 peak trains per hour. This means that my (and Devin’s, and Matt’s) proposed system allows more capacity even in the tunnel from Rosslyn to Foggy Bottom, which gets no additional connections the way 14th Street Bridge gets to feed a new Yellow Line trunk.
The big drawback of the plan is that the job center of Washington is Farragut, well to the west of the Yellow and Green Lines. WMATA makes origin-and-destination data publicly available, broken down by period. In the morning peak, the top destination station for each of the shared Blue and Yellow Line stations in Virginia is either the Pentagon or Farragut; L’Enfant Plaza is also high, and some stations have strong links to Gallery Place-Chinatown. Metro Center is actually faster to reach by Yellow + Red Line than by taking the Blue Line the long way, but Farragut is not, especially when one factors in transfer time at Gallery Place. The saving grace is that eliminating reverse-branching, turning Metro into four core lines of which no two share tracks, allows running trains more frequently and reliably, so travel time including wait time may not increase much, if at all.
This is why I am proposing the second alternative for the route between L’Enfant Plaza and Union Station. Devin proposed roughly following the legacy rail line. In the 1970s, it would have been better for the region to electrify commuter rail and add infill stops and just run trains on the route, and today a parallel route is appealing; Matt even proposed using the actual rail tunnel, but, even handwaving FRA regulations, that would introduce schedule dependency with intercity trains, making both kinds of trains less reliable. This route, the southeastern option among the two depicted in dashed lines, is easier to build, in that there are multiple possible streets to dig under, including C and E Streets, and giant parking lots and parks where the tracks would turn north toward the Capitol and Union Station. It also offers members of Congress and their staffers a train right to the officeUnfortunately, it forces Farragut-bound riders to transfer to the Orange Line at L’Enfant Plaza, slowing them down even further.
The second alternative means the Yellow Line stays roughly where it is. Four-tracking the shared Yellow and Green Line trunk under 7th Street is possible, but likely expensive. Tunneling under 8th Street is cheaper, but still requires passing under the Smithsonian Art Museum and tunneling under private property (namely, a church) to turn toward H Street. Tunneling under 6th Street instead is much easier, but this is farther from 7th Street than 8th Street is, and is also on the wrong side for walking to Metro Center and points west; the turn to H Street also requires tunneling under a bigger building. By default, the best route within this alternative is most likely 8th Street, then.
A variant on this second alternative would keep the Red Line as is, and connect the Yellow Line to the subway under H Street and to Largo. This is easier to construct than what I depict on my map: the Yellow Line would just go under H Street, with a Union Station stop under the track and new access points from the tracks to a concourse at H Street. This would avoid constructing the turns from the Red Line to H Street next to active track. Unfortunately, the resulting service map would look like a mess, with a U-shaped Red Line and an L-shaped Yellow Line. People travel north-south and east-west, not north-north or south-east.
Under either alternative, H Street would provide subway service to most of the remaining rapid transit-deprived parts of the District west of the Anacostia River. Some remaining areas near the Penn and Camden Lines could benefit from infill on commuter rail, and do not need Metro service. The big gaps in coverage in the District would be east of the river, and Georgetown.
Georgetown is the main impetus for the Blue Line separation idea; unfortunately, there’s no real service need to the east, along K Street, so the separate Blue Line tunnel would be redundant. In the 1970s it would have been prudent to build a Georgetown station between Foggy Bottom and Rosslyn, but this wasn’t done, and fixing it now is too much money for too little extra ridership; Bostonian readers may notice that a similar situation arises at the Seaport and BCEC, which should be on the Red Line if it were built from scratch today, but are unserved since the Red Line did not go there in the 1900s and 10s, and attempting to fix it by giving them their own subway line is a waste of money.
East of the river, the Minnesota Avenue corridor would make a nice circumferential rapid bus. But there are no strong radial routes to be built through it; the strongest bus corridor, Pennsylvania Avenue, serves a small node at the intersection with Minnesota and thereafter peters out into low-frequency branches.
This means that if the Yellow Line separation I’m proposing is built, all parts of the District that could reasonably be served by Metro will be. If this happens, Metro will have trunk lines with frequent service, two not branching at all and two having two branches on one side each; with passengers from Alexandria riding the Yellow Line, the Orange crush will end. The main issue for Metro will then be encouraging TOD to promote more ridership, and upgrading systems incrementally to allow each trunk line to carry more trains, going from 26 peak trains per hour to 30 and thence 36. Washington could have a solid rapid transit skeleton, which it doesn’t today, and then work on shaping its systems and urban layout to maximize its use.