Abstract: A wiring system for a vehicle is specified, which has a voltage source and an electrical load, whereby a need for the electrical load depends on an external condition. Furthermore, the wiring system has a load path with an electrical line, which connects the voltage source to the electrical load, and a first switching element, which is arranged in the load path, for disconnecting the electrical load from the voltage source, wherein a working range of the external condition is defined, within which the function of the electrical load is reasonable, and a control unit is arranged, which is designed in such a way that a switching on of the electrical load is prevented if the external condition lies outside the working range. Furthermore, a method for the design of an electrical line of such a wiring system is given.