Could it be that some signs are quantumly determined, collapsing to a state of true or false when you observe them? Based on his observations, Neill Jones thinks that it could.
He gives the example of a sign outside his house saying "No dog fouling". Every time he has looked at it, he says, it has been true. This is also the case with another "No dog fouling" sign on a building a couple of streets away.
On the other hand, on Salisbury Plain in the south of England, where there are regular military manoeuvres, there is a sign by the road saying "Tank crossing". This, says Neill, has collapsed to false every time he has looked at it.
There are, however, further complexities to this phenomenon. Some signs avoid a quantum collapse altogether, Neill notes. Take the "Gap ahead closed" sign he saw recently while driving up a dual carriageway (divided highway). If there was a gap ahead, he reasons, then it wasn't closed. If it was closed, then there wasn't a gap ahead. So the sign failed to be either true or false and was merely self-cancelling.
"Maybe I should get out more," Neill suggests. "But then I'll only find more signs. So maybe I should stay in more."
[New Scientist; 22 August 2009]