A power distribution system is provided that ensures that a car is able to operate safely in an autonomous mode. The system includes multiple power rails, including a pair of safety critical power rails. Associated with each safety critical power rail is a safety switch, vehicle sensors (e.g., vehicle location and obstacle sensors), vehicle actuators (e.g., braking and steering actuators) and an autonomous control unit. If a fault is detected during vehicle initialization or general operation, the safety switch which detected the fault opens and that particular power rail is decoupled from the general purpose power rail as well as the remaining safety critical power rail. The remaining safety critical power rail is then able to provide power to a sufficient number of sensors, actuators and controllers to allow the car to safely and autonomously complete an emergency stop on the side of the road.