Actually you're not the only one who has thought about that lol. The only catch is, power would most likely be out. So if you had to make a ammo/food run, and you ran out of gas (since those trucks drink it) you'd be screwed. But ya, would be pretty fun posting up on a roof and getting a some sniping hours in. Nothing better than shooting at innocent people turned zombie because they were in the wrong place at the right time