Speed Bumps

I was so amused by Harnser's great idea in the comments, I thought I would post it here incase anyone didn't read it. I doubt I will be able to look at a floating plastic duck or shopping trolley in the same way again!

"Speed Humps are what you need, a couple of shopping trollies positioned correctly with little plastic ducks floating above them, if they are going slow enough they can get round the little ducks, to fast to turn then its full stop with the bows 3" higher than normal."