Globally, 1.19 million people lose their lives annually in the road transport system, and around 10 million people are severely injured. Motor vehicle crashes resulting in soft tissue neck injuries, referred to as whiplash injuries, are the most common and costly disabling injuries for vehicle occupants. Injury statistics show that seat design plays an important role in the protection from these injuries in low severity rear impact crashes. In addition, the injury protection varies based on occupant sex. Relatively, most car models provide better protection for males, although that is not always the case. The hypothesis of this study was that vehicle seats that have shown different real-world performance regarding whiplash protection between female and male car occupants can be identified in crash tests with crash test dummies representing both sexes of the population. In the assessment of occupant safety, both in regulation and consumer tests, the average male model represents the average adult occupant. In this study an average female and male crash test dummy was used in tests at 16 km/h in two different seats (Saab 9-3 and Audi A4), which had shown significant differences in neck injury protection performance for females and males in real-world injury crashes. The results showed noticeable differences in the dynamic responses, highlighting that evaluation results for one dummy sex, exclusively, are inadequate for providing insights into the dynamic response of the other. This is the world’s first published study using average size, mass, geometry and dynamic properties models of the two main types of the adult population, females and male, in the assessment of injury protection in a crash and showing the link between real-life injury outcome and assessment of safety performances pointing to the future of how a more robust assessment of occupant safety can be achieved to further reduced the loss of life and health in the road transport system.