The Folk Process must have created the streamlined version I heard at school. The tune we used was The Policeman's Song from "The Pirates Of Penzance". So much for music lessons.

Please refrain from urination
While the train is in the station
Other people would not like it, nor would you;
Railway workers underneath
Get it in their hair and teeth
Other people would not like it, nor would you.

Warning: Do NOT attempt to sing this ditty as it will stay with you for life, and drive you mad.