Metro recently released data showing where Metrorail riders go from each station, and as one of our commenters noted, the most-frequented destination for people traveling from Anacostia is… Anacostia. That’s because Coast Guard employees and contractors use the Anacostia Metro as a pedestrian tunnel.

Entrance and exit through the same station by volume in October 2014. Image by the author.

As commenter Andy pointed out, when a passenger enters at Anacostia during midday, afternoon peak, and evenings on weekdays, they’re most likely to exit from the same station. Not only that, but as the chart above shows, entering and exiting at the same station is more common at Anacostia than at any other station in the system. Why?

At St. Elizabeths, where the Coast Guard’s headquarters moved in 2013, the National Capital Planning Commission’s parking policy allows one parking space for every four employees. That means the Coast Guard is limited to only 931 parking spaces for its 4000 federal employees and numerous additional contractor employees.

Unlike at NIH, the St. Elizabeths campus is over a mile walk from the closest Metro, there are no nearby parking lots, and street parking is limited.

The A4 bus, which leaves from the Anacostia Metro bus bay, runs directly to the campus. So many people who work at St. Elizabeths park in the 800-space garage at the Anacostia Metro, tap into the system at the garage entrance so they can walk through the station, and tap out at the exit closer to the bus bay. From there, they take the A4 to work.

The walking path from the Metro garage to the bus bay. Image from Google Maps.

It’s not hard to understand why commuters might opt to use the Metro station as a pedestrian walkway. While the walk down Howard Road from the parking garage to the bus bay is less than a quarter of a mile, it requires commuters to walk an empty stretch of road, under I-295 and across a highway on and off ramp.

The walking path from the Metro garage to the bus bay. Image from Google Maps.

The accidental pedestrian tunnel won’t be around for much longer. In the 2014 Coast Guard Transportation Act, Congress overrode the NCPC. Between now and 2017, the Coast Guard will be required to allocate an additional 1,000 parking spaces at St. Elizabeths.