Anton Dubrau of the Transit App team describes how they've cracked the problem of generating good-looking transit maps:
This is a problem that's intrigued me quite a bit, as I ponder how to meaningfully displace coincident lines and generate nonexistent out-of-scale curves for transit routes, in a cartographic world that's focused on ever-more-precise shapefiles as the answer to all problems. I hope to soon demonstrate an alternative way, at least for the Chicago region.
Alas, Dubrau's approach seems far beyond my capabilities, and seems a bit like using a chainsaw to carve a candelabra. But, then, so did GIS for its first decade.