This strange map recently appeared in Powell BART station:
Forward is to the left because that’s the way the train goes, as seen by a passenger facing the map. What’s strange about it is that the minor branchings are true to topology but the major branching is not: the rightmost path, which ought to be on top, is to Fremont (green), followed by Dublin (blue), Pittsburg (yellow), Richmond (red).
Perhaps the designer originally intended to include the Fremont-Richmond line (orange), which on this diagram would fit like a lining within the major fork. That would make the chart more useful, because after 7 pm and on Sundays the red and green lines don’t run: to get to Fremont or Richmond from Powell, you must switch from blue or yellow to orange.