How many Metro trains can fit through the tunnel under Rosslyn?

July 7, 2014

@LowHeadways brings up an excellent point on this piece that ran in Sunday’s Washington Post about the impact Silver Line service will have on Blue Line riders.

Here’s the graph that is the subject of the tweet:

There are only two ways across the Potomac River for Metro trains traveling between Virginia and the District. Yellow Line trains go over the Yellow Line bridge; Blue and Orange line trains move through a tunnel below Rosslyn in Arlington. The tunnel can accommodate 26 trains an hour. The start of Silver Line service means Metro has to open up some slots in the tunnel.

This is true. The Rosslyn tunnel could accommodate additional trains, but 26 is the number that Metro officials think the system can accommodate without having an adverse impact on service.

According to Metro spokesman Dan Stessel: “Twenty-six trains per hour is the maximum for reliable service. While there are in places certain components of the system that might have a higher capacity, operating trains more frequently than every 2 min 15 sec would result in a degradation in reliability (i.e. trains holding in tunnels with nowhere to go).”

Thanks for noting this @LowHeadways.

Lori Aratani writes about how people live, work and play in the D.C. region for The Post’s Transportation and Development team.
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