Tarmac joke?

A bit of tarmac goes into a bar "give me a pint" he says "I'm hard""Ok" says the barman. Just then a red bit of tarmac comes in "give me a pint I'm harder than him, I have busses roll over me" "Ok" says the barman. Just as he puts the pint down a green bit of tarmac comes in and the black and red bits of tarmac jump over the bar and hide "What you doing that for?" the barman asks "You don't mess with him" the tarmacs reply "he's a cycle path"