Showing walk times on transit maps

Because transit system maps are a rendition of the system that isn't mapped exactly to scale, people unfamiliar with the system may not know that certain stations are better for certain destinations than other, that it is faster to walk from a particular station to your final destination rather than take the time to transfer to another line to get to the seemingly closest station, etc.("8 London Tube journeys that are quicker by foot," London Evening Standard).  From the article:

Leicester Square to Covent Garden. Have sympathy for the person that queues for 15 minutes to get into Covent Garden station, waits another five for the lift and boards a packed tube to Leicester Square at rush hour, when they are only 250m away from one another.

People have created such walk time maps for the London Underground and Toronto subway systems.

Transport for London created an official walk time map last fall ("TfL has released the first official 'walk the Tube' map for London," London Evening Standard).

A professor at Queens College has created such a map for the Toronto subway system ("Map shows walking times between TTC subway stops," BlogTO). In the Downtown core, it's faster to walk between the west and east legs of the subway than to stay on the train.

Because the WMATA system is more of a hybrid between a commuter railroad in the suburbs and a subway system in the core of the region, and because outside of DC's core, most areas aren't served by a criss-cross network of transit lines, like New York City, London, or Paris, and so the walk times between stations aren't so relevant at every point on the system.

But in the core, especially in the Central Business District, knowing walk times between stations would make sense.

Like in London, it's easier to walk between lines at some places than to transfer between lines, such as Metro Center to Gallery Place or Farragut West to Farragut North (since 2011 people have been able to exit from one station and walk to the other to transfer between different lines and get back on without paying a separate fare).

While a longer walk, maybe rather than deal with crowds at the Navy Yard station after a Washington Nationals baseball game, it'd be easier to go to the Capitol South Station, especially if you would be riding on the Blue/Orange/Silver Lines anyway.  It's six-tenths of a mile, or just a bit longer than 10 minutes.