(NZ here) The signs don't get mirrored. They could show up on straight roads, but are much more common in places with corners. I've always interpreted it as a

(NZ here) The signs don't get mirrored. They could show up on straight roads, but are much more common in places with corners. I've always interpreted it as a cartoony car version of what your legs do when slipping on ice - sliding out from under you in random directions.