In fatal accidents more than 60 percent of the injuries are to the head and neck, and almost all other fatal injuries are to trunk. Detailed investigations by the road research laboratory into about 500 accidents showed that roughly two-thirds of these accidents involved frontal collisions /i.e., within 45 degrees of straight-ahead/, about 12 percent were to the sides of cars and about 7 percent were rear-end collisions. Thus the most important problem is how to protect the heads and bodies of occupants in head-on collisions. This is the primary purpose of a seat harness. An attmept is made to calculate approximate maximum values of the forces and decelerations to which a person held in a seat harness is exposed in a head-on impact. Formulas are presented which indicate the effects of the variables involved. A harness that yields at a predetermined load by having a very stiff or almost inextensible harness attached to the vehicle through a link that yields when a predetermined load is reached, movement then taking place against a constant force, was investigated. Harness of the yielding type could be effective in head-on impacts at speeds up to nearly 50 mph, without subjecting the passengers body to excessive forces and without stretching more than 1 foot. This is probably about 15 mph more than existing elastic harnesses will withstand. The stiffness of harness materials varies considerably, as does harness design.
Abstract