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Randall Munroe
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What would it look like if we all put aside our differences, beefed up our infrastructure, and connected North America’s existing subway lines into a pan-continental Voltron subway — a Voltrain, if you will — running from Far Rockaway to Redondo Beach and from Mexico to Montreal? Randall Munroe of XKCD has a map, plus some secret innovations (look for the Puerto Rico submarine shuttle).

What’s striking about this, besides how pathetic Baltimore is (hi, Baltimore, I love you), is the fact that there would be no coverage west of Chicago until you hit California. Not a single city in the Mountain time zone, and only one in Central, has a subway fitting Munroe’s definition (“a network containing high capacity grade-separated passenger rail transit lines which run frequently, serve an urban core, and are underground or elevated for at least part of their downtown route”). If you go by landmass percentages, an all-North-America subway made by connecting existing subways would do just as crappy a job covering everyone as Baltimore’s sad excuse for rail.