The thing about station numbering is (a) they’re essential navigational tools for people unfamiliar with the system (especially if they’re also unfamiliar with the local/national language) and (b) they work best when one pair of tracks on the ground carries only one rail service. Washington, DC gets a lot of tourists, so a station numbering system would be useful (Japan uses them even on small, uncomplicated systems like the Nippori-Toneri Liner), however, very often two or three routes have to share one pair of tracks, which complicates the process of actually designing it somewhat.
This is only a first draft; there are probably a bunch of ways to make the system more intuitive but here’s what I got so far after about a week of intermittent thought:
I included the Purple Line because I have no idea exactly how well it would integrate with the existing Metro system, and better safe than sorry. It works just like any other station numbering system you care to name: you start with “1” at one terminal and count up till you reach the other terminal. The letter before the station number generally corresponds to the line serving that station (e.g. Woodley Park is the 12th station on the Red Line, and is therefore assigned the code “R12”), but where one station serves two or more lines, the assigned letter either goes to whichever line is more frequent (“G2” at College Park), or which line was open longer (“B22” at Crystal City). Orange Line stations are assigned the letter “A” for obvious reasons.
Here’s how the signage would look from the traveler’s perspective:
The specifics of the strip map (e.g. station spacing and design) might change, but the basic design is there. We have the station number prominently displayed next to its name, as well as (something I snafu’d from Japanese signage) the name, number, and direction of the next station over (that last bit is key, as it allows the passenger to orient themselves better).
My only concern is what would happen if, say, the Red Line were extended from Shady Grove, the Green Line from Greenbelt, or the Blue/Silver Lines from Largo. (The Taipei Metro uses station numbering; the station marked BL1 is not and never was the terminus for Line 5—once known as the Blue Line—the next station over is BL40. I find this confusing.) However, I don’t think this is anything worth losing sleep over, since the SV extension to Dulles and Ashburn will probably be the last new construction Metro will see for a very long time.
Hopefully this little plan will at least start to address the challenges inherent in a station numbering system for the DC Metro, and hopefully the more thought is put into it the more comprehensible it’ll become.