Exploiting inaccuracies

Normally there's a certain degree of inaccuracy in data visualization--the purpose is not just to present all the information, but to make it somehow legible. In the case of transit maps, that involves twisting actual geography to make the patterns of transportation clear (think of how short and squat Manhattan is in the MTA map). Sometimes it's possible to take these inaccuracies of design and exploit them to make new things: here, webcomic xkcd treats various transit maps as having literal geography, splicing them together into one giant north american network (with a few creative inclusions).

 source: https://xkcd.com/1196/ 

source: https://xkcd.com/1196/