Well, I'd argue parking spaces are special: because they can be turned into free space, and then turned back into a parking space, very easily! Sometimes you do

Well, I'd argue parking spaces are special: because they can be turned into free space, and then turned back into a parking space, very easily! Sometimes you don't even have to do anything - for proof, see parking restrictions intended to free up extra lanes during busy periods, that rely on nothing more than the time of day. This makes the experiment quick and easy to do. (You could also knock down a shop to see what would happen, but that would be harder to reverse, and the owner would be unlikely to agree to it.)