Don’t make your survival plans dependant on infrastructure too much, it may not be there. The police may be too busy, fire fighters probably won’t come into a war-zone just to get shot at. Electricity can easily be interrupted by a bullet into a transformer. Home and cell phones can fail, be overwhelmed or be taken out by a rioter.

While these things are probably going to be short lived, they could be nasty (ask Reginald Denny) and you have to expect that the only one looking out for you is you.