Characteristics of Human Responses in a Braked Stationary Lead Vehicle during Low-Speed, Rear-End Collisions

The main aim of this study was to identify whether braking force applied to a stationary lead vehicle in low-speed, rear-end collisions should be considered for whiplash injury mechanism assessment and safety system development. A three-dimensional motion capture system with eight infrared cameras and a wireless surface electromyogram were used to quantify the kinematic, moment, and muscle activation characteristics of the neck joint during low-speed, rear-end collision tests. The maximum angles of the neck joint did not differ significantly during the tests with and without the applied braking force during low-speed, rear-end collisions (p > 0.05). However, the angular velocity of the neck joint with the braking force applied was higher than without the applied braking force (p < 0.05). The maximum moments of the neck joint when the braking force was applied were generally 1.4 ± 0.2 times higher than those without the braking force (p < 0.05). The muscle activations of the sternocleidomastoid and splenius capitis under braked conditions were 1.2 ± 0.1 and 1.5 ± 0.2 times higher than those without braking, respectively (p < 0.05). The results indicate that braking force applied to the stationary lead vehicle during a low-speed, rear-end collision should be considered for whiplash injury mechanism assessment and safety system development.