h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

You get the WRONG WAY! signs on American roads too.

I always wondered how they knew where I was trying to go in the first place...

Australian "WRONG WAY GO BACK" signs are usually placed on a freeway exit, facing away from the correct flow of traffic. If you don't do anything wrong you will never see this sign. Australia has a large number of tourists from Europe and the US,and since we drive on the left, there have been some incidents where a tourist has entered a freeway on the exit, and been hit head on at 100km/h. The best thing to do if you come face to face with one of these signs is reverse as fast as possible, and hope for the best.

So why do the Americans have them I wonder? (They're also on freeway exits there.)

Mind you in the UK you'd be surprised how many people will reverse up an entry slip road to a motorway when they realise they've taken the wrong turning - an equally stupid thing to do! So maybe they're there to protect against native stupidity just as much.