When is a model release required?

I wanted to know if any of you could help me understand when a model release is required. I am going to be creating some industrial stock footage ie. refineries, transit stations, freeways etc. and I was not sure what the rules were for people in the shots. Some of the shots will be taken from adjacent buildings and at odd angles to make for more interesting shots and I doubt the actual faces will be able to be individually identified. Any help on this issue would be greatly appreciated.

First and foremost read review footage requirements. If you shoot Toco Bell, Buger King or McDonell resturants those businesses have logos, which require a property release. Actors,TV personalities and statesmen require a model release. Otherwise all those clips will be considered for editorial use only. Look at the shots of Las Vegas to see how many of those can only be used as editorial only.

jason