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A methodical investigation and measurement of human dynamic response to impact acceleration is being conducted as a Joint Army-Navy-Wayne State University investigation. Details of the experimental design were presented at the Twelfth Stapp Car Crash Conference in October 1968. Linear accelerations are being measured on the top of the head, at the mouth, and at the base of the neck. Angular velocity is also being measured at the base of the neck and at the mouth. A redundant photographic system is being used for validation. All data are collected in computer compatible format and data processing is by digital computer. Selected data in a stage of interim analysis on 18 representative human runs of the 236 human runs completed to date are presented. Review of the data indicates that peak accelerations measured at the mouth are higher than previous estimates.

An acceleration sled carrying living human subjects was used to measure the dynamic response of the head and neck to —G x impact acceleration. Seated volunteers with complete pelvic and upper torso restraint were subjected to increasing impact accelerations beginning at 2.7 g and increasing in 1 g increments. The volunteers were selected to encompass the 5th to 95th percentile distribution of sitting height according to a selected reference. Precision inertial transducers were used to determine the linear and angular acceleration of the head and the first thoracic vertebra. The inertial system consisted of a biaxial accelerometer and rate gyroscope on a bite-plate, a biaxial acceierometer over the bregma, and a biaxial acceierometer and rate gyroscope over the spinous process of the first thoracic vertebra. The transducers on the bite-plate and over the bregma were rigidly connected to one another.

The kinematics of rear-end collisions based on published acceleration pulses of actual car-to-car collisions (10 and 23 mph) were reproduced on a crash simulator using anthropomorphic dummies, human cadavers, and a volunteer. Comparison of the responses of subjects without head support were based on the reactions developed at the base of the skull (occipital condyles). The cadavers gave responses which were representative of persons unaware of an impending collision. The responses of both dummies used were not comparable with those of the cadavers or volunteer, or to each other. An index based on voluntary human tolerance limits to statically applied head loads was developed and used to determine the severity of the simulations for the unsupported head cases. Results indicated that head torque rather than neck shear or axial forces is the major factor in producing neck injury.

Both the inverted-Y yoke torso harness with inertia reel and the air bag restraint system have had extensive independent development for some time by several engineering and research organizations for both aviation and ground vehicle occupant protection. The research reported in this paper consists of the first biomechanical primate evaluation of these concepts as experimentally adapted for possible automotive use. These tests are a continuation of a study involving the relative impact protection and effectiveness of major restraint systems utilized in general aviation aircraft and in limited automotive use. The objective of this test series was to determine how much protection those advanced restraint concepts provided; to obtain preliminary biomechanical and physiological data; to identify problems of technique and applications in occupant protection; and to provide an initial basis for direction of future test requirements.

This SAE Information Report provides data regarding human tolerance to impact conditions. This information is based on currently available knowledge and experience in the biomechanics field. However, in utilizing the information set forth, it must be recognized that both experience and data in the field of biomechanics are limited and, in some cases, unrefined. It is intended that all portions of the report be subjected to continuing review and that it be revised as additional knowledge and experience would warrant.

An attempt to summarize and correlate the possible injurious mechanisms occurring in whiplash and head injury by impact is presented. The relation between whiplash and cerebral concussion has been investigated in two ways. First, it is demonstrated that a collar restricting bending and twisting but not stretching of the neck, as well as reducing rotational acceleration of the head, significantly raises the threshold for experimental cerebral concussion produced by occipital blows to the freely moveable head in monkeys. Secondly, experimental whiplash without head impact in the monkey can produce significant reduction of standard responses to external stimuli. It is suggested that multiple mechanisms are involved in cerebral concussion, among them rotational acceleration of the head, flexion-extension-tension of the neck and intracranial pressure gradients being probably the most significant. The direction of future investigation is indicated.

Fatalities in various modes of transportation are reviewed, with the point being made that distance death rates must decrease as mankind's average trip distances increase. The multiple origins of airbag restraint concepts are traced. The possibility is presented of having no restraint other than the seats prior to a crash situation, then automatically inflating transparent chest airbags to “grab the wife and kids” if a crash is developing. The driver would wear a lap belt and shoulder Straps. The bags would automatically deflate after the crash. Analytical models of automobile crash loads, and of passenger motions in the airstop restraint, consisting of a chest airbag and an inflated “airseat,” are reviewed, with emphasis on rear and side collisions. For higher speed crashes, additional protection is suggested by using a 10,000 pound loop strength lap belt on the airseat, and within 0.03 seconds after impact preloading the chest airbag to a higher pressure proportional to speed.

Development is progressing of an improved airbag restraint system for passenger vehicles which we call “airstop.” It consists of an airbag in front of the chest, an airbag in front of the feet and under the seat, and an inflated airseat. This system has an impact load transmission to the subject of one-third or less of the vehicle longitudinal or vertical loads. The experimental work leading to the airstop design is reviewed, with acceleration data presented for vertical and inclined drops of the initial full-length airbag system and an astronaut airbag restraint system, swing and drop impacts of airstop systems, and a DC-7 crash test of a chest and foot airbag system. The airstop system is designed for automatic deflation of the bags and the seats after a crash, greatly facilitating fire escape from the aircraft. The weight of the airseat system is less than the weight of present seats.