Interestingly, when pedestrian crossings were being introduced in the UK it was decided that a statement like 'DON'T CROSS' was problematic. There was no legal basis on which pedestrians could be prevented from crossing a road and the instruction was therefore being given without due authority! The town council had no right to tell a law-abiding Englishman not to cross the street! So, we got the 'Green Man' signs intead, and of course there is still nothing preventing you from crossing the street wherever you wish here in the UK. Another interesting snippet was the fact that in East London it was thought that signs on crossings would not work due to the large number of Russian immigrants, since "[...] these people are excitable and ill-disciplined." See this article for more information http://www.cbrd.co.uk/articles/pedestrian-crossings/