In modern cars, driver assistance systems more and more increase both convenience and safety. Many of these systems reduce the possibility of human errors, which still are the main cause of accidents. Recently, self-driving cars can in most situations even operate without any direct human control. This way, much of the responsibility for preventing accidents moves from the driver to the car – and, thus, to the manufacturers and their suppliers. This means that the functional safety of cars becomes more important than ever. For this reason, all safety-critical systems of a car need to be developed according to ISO 26262, which defines mandatory requirements for the development process. This article explains how requirements traceability can help to fulfill these requirements successfully and sustainably.