The study looks at seating systems with respect to the seat belt loading characteristics and occupant kinematics in frontal and rear impacts to determine if improvements can be made with respect to major injury criteria of the occupant in lay-down style IRL cars. The study compares the seat belt loading characteristics between upright stock car seating positions and lay down seating position of an IRL car. This is being done because of the differences that have been seen in lower back injuries between the two types of seating positions.
Three safety systems (V1, V1a, and V2) have been engineered to study the possibility of improving the system performance using basic restraint system principals. The study compares current IRL systems to 3 progressively more experimental safety systems using seat changes, a knee bolster airbag, lap belt pretensioners, lap belt load limiting and upper torso control utilizing seat belt elongation as a load limiter and head and neck restraint.
The basis of the series is to begin restraint of the pelvis as early in the event as possible. Decreasing the pelvic acceleration and utilizing the available space can better control the torso loads and thus the head and neck loads in frontal impacts. Lower pelvic and chest loads along with modified occupant kinematics should translate into decreased loads on the lumbar spine area where injuries have been seen in the field. A modified hybrid III dummy was used in the study. The modified Hybrid III did not allow for the use of a lower lumbar load cells to determine if the loads were reduced directly. Therefore, some assumptions must be made in this area.
IRL cars accommodate a reclined seating position. During severe rear impacts in these seating systems, the occupant tends to rise in the seat, exposing the head over the head rest. Late in the event, the knees rise into the cockpit hitting the back of the steering wheel. The goal in an improved system is to, not only benefit the occupant in frontal impacts, but also to reduce the amount of upward movement and to keep the legs restrained in the foot well in rear impacts also. This is accomplished by using modified sub belt positions, buckle pretensioners and a knee bolster airbag.