Devices for the protection of car occupants during car collisions are being continuously improved and developed. The motivations for this never ending activity are not only to meet the safety design rules and standards, but even more to satisfy the increasing demands of consumers and to meet new challenges of competitors to be counteracted.This paper describes a numerical procedure for the optimisation of an existing restraint system including an OEM's airbag in front collisions. The solution process was systematically divided into four steps: 1) development of a computer model for the computer code MADYMO, 2) validation of the model by comparing the numerical and experimental results, 3) investigation of sensitivities of injury criteria to design changes, and 4) optimisation of the restraint system and airbag for minimum injury.The results indicate that the OEM's driver-side airbag and the existing restraint system can be substantially improved. By optimising the airbag and the restraint system separately, the overall injury levels are reduced by 17% and 9% respectively. When the airbag and the restraint system are optimised together, a 33% reduction of overall injury level has been, achieved. It reveals that the airbag and the restraint system have to be tuned together to achieve the maximum safety performance.