Or else.....

I park near this sign when I hop over the railway most mornings on my way to the beach.

I've had my eye on it as a backup blip for a while. It makes me smile. What sort of trouble do they think your wheels are going to get into if you don't curb them...? I always wonder if I'll return to find them lying sideways off the car, having had a punch-up with each other, empty beer bottles strewn around.