Also its going to be impossible for zombies to get survivors. And when survivors stack/hoard all ammo to parking lot and camp there, zombies have even smaller possibility (impossoble x8) to get survivors. I suggest, like others, add cars to that parking lot. There can be lots of cars on that parking lot. Add first lots of cars, and if it starts lagging, reduce the amount of cars until that parking lot are runs fine. No one wants to play map which is unfair for one team.
For the looks I see, it's okay for now.