Here in New York City, the MTA regularly reminds us subway riders of certain dangers in the system. Using posters featuring simple Helvetica text and sometimes stick figure illustrations, they warn us against things like riding outside the train, and venturing onto the tracks.
From the mid-'70s through the early '80s, the Toyko subway system also used posters to remind riders of the rules, except these featured super heroes, Hitler, aliens, Santa Claus, even Jesus Christ. The posters warned against more specific, but possibly annoying, behavior. Aliens told riders to not read newspapers too widely, Hitler and Charlie Chaplin illustrated the evils of spreading your legs too far apart while sitting, Jesus told you not to forget your umbrella, and Santa Claus reminded riders at the holidays not to get drunk and pass out on the train. [Images and translations from Retronaut via WFMU]