Communication networks in vehicles today serve a lot of non-safety-critical applications, like body electronics or comfort functions. Introducing safety-critical applications, e.g. brake-by-wire, steer-by-wire, etc., without any mechanical or hydraulic backup demands new requirements for the underlying communication system. This paper introduces these new demands, exercises the applicability of existing in-vehicle networks and analyses a new approach which is derived from various existing solutions of fault-tolerant communication systems in the field.