Passenger kinematics in evasive maneuvers

Doctoral thesis, 2023

Most drivers that notice an impending crash try to avoid it by performing an evasive maneuver, such as braking or steering. In response to the maneuver, the people inside the car move relative to the interior. In cases where the crash was not avoided despite the evasive maneuver, this movement relative to the vehicle could change the injury outcome of the crash, compared to if no maneuver had been performed. Because the maneuver could influence the injuries in the crash, it is important to consider maneuvers that occur before the crash to develop safer cars.

Simulation models of human bodies, vehicles, seat belts, and airbags are used typically to evaluate safety performance during vehicle development. Compared to physical testing, where relatively few tests can be performed, simulation models allow for thousands of virtual crash tests of the car and human during car development. These comparably inexpensive virtual tests allow for evaluation of more scenarios and braking or steering prior to the crash can be included.

In contrast to in crashes, humans can counteract the movement during maneuvers with muscle force. Thus, simulation models that evaluate the relative movement during maneuvers need to consider the muscle forces produced to counteract the movement. In this thesis, existing simulation models of car passengers that account for the muscle forces have been further developed to allow for more accurate modelling of movement during these maneuvers. The control systems that regulate muscle force production in the simulation model have been updated, and the parameters of the control system have been tuned such that the simulation model's movement during braking and steering simulations is as close as possible to how an average human moves during braking and steering.

Additionally, physical tests with human volunteers in a vehicle have been analyzed to understand how humans move during braking and steering. In that analysis, it was found that there is a large difference between how different people move during braking or steering. A statistical analysis was conducted to investigate if there were systematic differences between how males and females, shorter and taller people, lighter and heavier people, and younger and older people moved. It was found that only small systematic differences were present in the tests, and even after accounting for these differences, large variability remained. Therefore, the simulation models of humans were used to identify if other systematic differences could explain the large differences. With these simulations, it was found that some effects could be seen when letting the human sit more upright or slouched in the seat and when moving the seat backwards or forwards. The findings in this thesis suggest that future physical tests with human volunteers should investigate if sitting more upright or more slouched prior to a maneuver influence how people move during a maneuver.