Breaker boxes are found throughout the maps and generally need to be completed with a Circuit Breaker in order to open or close a gate or door.

The Circuit Breaker is a part that must be obtained in order to complete the circuit in a Breaker Box and open whatever gate or door it is attached to.

This option will not open up for you in the early part of your game, but once it does, travel around LA will get an awful lot quicker.

The Fusebox will need a Fuse to operate. You can find these throughout the map as you travel around.

A door that will open open with one of the many keys throughout the game, many of which are dropped by specific named zombies.

When it is time to travel between areas, the Zone Exit on the map is where you need to head to.