The urge to try and destroy the standing zombies by shooting them is very strong, and led to many a game over despite me understanding that's not how to deal with them!
My record is killing six of the ceiling guys before my inevitable demise. I found sticking to the middle road was the only safe way to avoid situations where zombies spawned directly on top of me for an instant loss. So sticking middle, shooting the tunnel droppers and only veering left or right when absolutely necessary is my strategy. :)