London has extremely cramped, extremely crowded stations. Platform screen doors become necessary as a way to ensure safety of _crowds_ not individuals. In most

London has extremely cramped, extremely crowded stations. Platform screen doors become necessary as a way to ensure safety of _crowds_ not individuals. In most metro stations around the world, this is not true. How about making a study, counting all metro stations noting whether they have platform screen doors, automation, and the year built. You'll very likely see there's a strong connection between automation and platform screen doors, but less so for the other variables.