A drunken man was wandering around the parking lot of a bar

A drunken man was wandering around the parking lot of a bar,
bumping into cars then rubbing the roofs of the cars.

The manager comes out of the bar and stops the guy.

'what the heck are you doing ?' he asks the drunk.

'i'm looking for my car, and i can't find it.' he replies.

'so how does feeling the roof help you ?' asks the puzzled manager.

'well,' replies the drunk earnestly, 'my car has two blue lights and a siren
On the roof!'.