The upcoming ISO26262 standard, which deals with the functional safety of road vehicles, will induce car manufacturers to adapt the way in which vehicle systems are usually developed. To achieve this, more rigorous development processes along with new tools and techniques will most certainly be necessary. This paper presents an overview of current initiatives at Renault dealing with the improvement of development processes for mechatronic systems to comply with ISO 26262. It focuses on introducing more formalization in the systems engineering design process via the definition of an ontology to formalize the concepts and knowledge of the systems engineering, functional safety and automotive specialty domains (e.g. braking, energy management). The ontology is at the heart of our improvement initiatives since it allows establishing logical consistency of the whole design process. A regenerative hybrid braking system integrated into a full electrical vehicle will serve as the case study for the evaluation of the improvements made possible by the approach.