A note from Neil Freeman: When I say the maps are in the same scale, each is drawn in a custom Transverse Mercator map projection centred on each system. I’ve defined “metro” as high-capacity urban heavy rail systems that run on grade-separated right-of-ways. They run with short headways, at least at rush hour, and are generally built to serve commuters. Further, the metros I’ve included have platform boarding (you might have to mind a gap, but you don’t ascend steps).
Since I’ve included “urban” systems, I’m excluding inter-city lines. I also exclude short systems that primarily serve as transit within a business district. There are, of course, grey areas. London’s DLR is an edge case, and I think that one could reasonably include it in this list. However, it has “light railway” right there in the name, so I think that distinguishes it from “heavy rail”. Seoul’s subway and commuter rail systems are intertwined in ways that are difficult to categorised, and I hesitate to say I’ve made the right choices there. The underlying data is from OpenStreetMap and is available under the Open Database Licence.
