Scientific methodology and engineering techniques were applied to a series of twelve automobile rear-end collision experiments to provide data relating to seat, seat backrest and head-restraint design. Five speeds of impact, six seatback heights and six seatback strength values were studied. The purpose was to evaluate the relative protective merits and the practicality of various seat designs with respect to the many variables common to rear-end collisions. This research data provides a basic reference system of collision performance for seat designs with respect to occupant size, posture and proximity to injury producing structures.