Six human volunteer subjects were used to analyze the effects of normal braking compared to forceful braking in non-impact stationary, non-impact dynamic, and vehicle-to-vehicle impact conditions. For the non-impact conditions, each volunteer performed normal and hard braking maneuvers with the vehicle stationary and in motion. Vehicle dynamics and occupant kinematics were measured during impacts and brake pedal force and displacement were measured in all conditions using a non-ABS equipped vehicle.
A series of twelve low speed rear-end crash tests were conducted with the same six human volunteers. Each volunteer was subjected to two rear-end impacts with an impact speed of approximately 12 km/h. In the first test, each volunteer was asked to apply the brake as though they were stopped at a stop light, and they were unaware at the time of impact. Then, each volunteer was subjected to a second test where they were braced and aware of the impending collision, while forcefully applying the brake. Brake pedal force and displacement on the target vehicle were measured during the collisions.
During the crash tests, the initial and maximum brake pedal forces were greater for all occupants in the aware condition. During impact, the brake pedal force and displacement initially decreased for all occupants in all tests, indicating foot movement away from the brake pedal. For all unaware tests, the brake pedal force went to zero, but did not go to zero in all of the aware tests. Seat belt forces were lower for all occupants in the aware condition, indicating that their internal musculature altered their subsequent forward rebound motion. The vehicle post-impact travel distance for the aware tests was always less than for the unaware tests.
Vehicle dynamics were dependent on the amount of brake pedal force, but brake pedal force was not consistently related to awareness and bracing. Braking in the unaware condition did not appreciably affect the vehicle or occupant kinematics.