If we cover the yellow line, we can put the line in a quantum superposition of states. Then, it's both yellow and not yellow at the same time! Now, I'm not sure how that would help. (Maybe we can confuse the board enough that they'll agree with our proposals.) But anyway, why can't we make a line that's shorter than the road. There's nothing that says that the line has to go all the way along the road, merely that the traffic has to be separated. Or, we could put a sequence of infinitely short yellow lines. The cars will always be separated by at least one, but the length is still zero.