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THERE ARE four viable types of glazing for use in motor vehicles: 1. Laminated 2. Tempered 3. Laminated glass-plastic 4. Tempered glass-plastic Laminated and laminated glass-plastic glazing will pass the MVSS Standard 205 for windshields, and all four types can now be used in side and rear windows. Laminated and to a limited extent laminated glass-plastic windshield glazing has been used in production, but the glass-plastic was not durable enough so it has been discontinued. Tempered glass has been used exclusively in side and rear windows since the early 1960's due to the strength requirements, and is the best choice for these locations. Recent experimental attempts to use tempered glass-plastic glazing in side windows have been unsuccessful due to high neck loads, and additional hazards in the designs. Even more important is the lack of durability due to more severe exposure than the glass-plastic windshield experienced.

Unembalmed cadavers restrained with a three point harness were exposed to a deceleration environment of 20, 30 and 40 mph BEV.* Injuries were tabulated from detailed autopsies. The results Indicate an AIS-1 injury at 25.5 mph, an AIS-2 injury at 31.5 mph and an AIS-3 injury at 34.5 mph. The AIS-3 injury level is recommended as the maximum acceptable injury. The cadavers sustained the same types of injury that have been reported in medical literature including bruises, abrasions, lacerations, fractures and viscera ruptures, but injury severities were greater in the cadavers than in living humans at a given collision severity. Also, there is a wide spread in the degree of injury between cadavers due to differences in age and physical condition. The threshold of cadaver rib fracture is 30 mph and the threshold of cadaver vertebral fracture is between 30 and 40 mph for the environment utilized. More numerous and severe abdominal injuries were observed.

A review of the existing mathematical models of a car occupant in a rear-end crash reveals that existing models inadequately describe the kinematics of the occupant and cannot demonstrate the injury mechanisms involved. Most models concentrate on head and neck motion and have neglected to study the interaction of the occupant with the seat back, seat cushion, and restraint systems. Major deficiencies are the inability to simulate the torso sliding up the seat back and the absence of the thoracic and lumbar spine as deformable, load transmitting members. The paper shows the results of a 78 degree-of-freedom model of the spine, head, and pelvis which has already been validated in +Gz and -Gx acceleration directions. It considers automotive-type restraint systems, seat back, and seat cushions, and the torso is free to slide up the seat back.

A combined program of accident investigation, staged collisions, and simulated collisions involving three-point harnessed occupants in frontal force collisions has provided a means of correlating injury with forces and/or other physical parameters associated with the injuries. With a strict screening to ensure complete data on each accident, 128 cases involving 169 occupants at barrier equivalent velocities from 2-53 mph were compared with the results from 11 staged collisions and 72 simulated collisions. There were 14 rib cage injuries ranging from single sternum fracture to seven rib fractures at velocities of 10-53 mph at injury levels of AIS 2 and 3. A single AIS 4 injury was the most serious injury and consisted of a ruptured spleen. The most serious brain injury was an AIS 2. Two cervical vertebra fractures were found, one of which was a 12-year-old male and the other a 76-year-old female. Only 14 occupants had AIS 3 injuries.

Five different restraint systems-mandatory harness, airbag + 20% lap belt usage, airbag, passive three point harness, and torso and knee bar-are analyzed for fatality and injury reduction, benefit/cost ratio, and cost-effectiveness. The mandatory harness is superior to the others in all comparisons with approximately 100,000 lives saved over the first 10 years which is about twice as many as would be saved by the other systems. A major advantage of the mandatory harness is that practically all of the vehicles are equipped while the other systems will require 10 years for complete installation.

A comparative study of the safety performance of asymmetric and standard HPR windshields was conducted. The effect of increased interlayer thickness was also quantified. There were four different types of asymmetric windshields which had inner layer thicknesses of 0.8 to 1.5 mm and interlayer thicknesses of 0.76 and 1.14 mm. The experimental program consisted of both full scale sled tests and headform drop tests. A total of 127 vehicular impacts were carried out using a modified Volkswagen Rabbit. The test subject was a 50th percentile Fart 572 anthropomorphic test device. The asymmetric windshields were found to have a lower lacerative potential than that of the standard windshield. The best TLI value of 5.2 was provided by a 0.8 - 0.76 mm windshield at 60 km/h. That for the standard windshield was 7.7 at the same speed. All HIC values were less than 1,000 at 48 km/h.

A series of carefully controlled simulated barrier crashes at speeds from 20 to 30 mph are used to compare the relative safety of rubber gasket, butyl tape and polysulfide adhesive methods of installing windshields. Only subtle differences were found in the severity index and the laceration index. There is an indication that the rubber gasket installation has a higher resistance to interlayer tears and the lacerations from impacts to polysulfide installations are slightly more severe. Head attitude at impact was found to have a significant effect on interlayer tears and resultant lacerations.

Conventional 30 mil HPR laminated and wide-zone monolithic tempered windshields are compared on a safety performance basis from the stand-points of occupant injuries from frontal force collisions and injury or loss of control from breakage from high speed external impact of stones. All experiments were conducted with the windshields installed by conventional methods in an automobile. Occupant injury potential as measured by the Severity Index for brain damage at a 30 mph barrier impact simulation was approximately two times as high for the tempered as for the laminated windshields, although only one tempered windshield exceeded the recommended maximum value of 1,000. Severe lacerations resulted in all impacts in which the tempered glass broke. Less severe lacerations were found for the laminated windshield impacts at comparable speeds.

A voluntary increase in usage of restraint systems can be achieved by educating the driving public to their advantages and by improving them by the addition of self-storing inertia reels, easier identification of mating parts, automatic adjustment, improved anchor location, and more convenient methods of buckling. Finally, mandatory use of present upper torso and lap belt restraint systems through legislation would show a step decrease in injuries and fatalities. A foolproof interlock between the restraint system and the ignition system is an alternative to legislation.

Data are presented for 19 frontal-force collisions involving vehicles with collapsible steering columns with collision severity rating from minor to very severe (1–7) and an injury severity index from minor to fatal. Injury results are compared to laboratory experiments in which a force of 1800 lb distributed over the rim and hub was measured for a fairly stiff wheel and collapsible column combination. When the steering wheel did not deform excessively and the force reached the 1800 lb level as evidenced by column collapse, there were no serious thoracic injuries. Gross deformation of the steering wheel with exposed sharp spoke ends or small diameter hub resulted in serious abdominal and thoracic injuries. Two cases of hood intrusion are presented, each of which resulted in fatalities.

Human tolerance to knee, chest, and head impacts based upon skeletal fracture of cadavers is reported. The results are based upon unrestrained cadaver impacts in a normal seated position in simulated frontal force accidents at velocities between 10 and 20 mph and stopping distances of 6-8 in. The head target was covered with 15/16 in. of padding. No skull or facial fractures were observed at loads up to 2640 lb. Extensive facial fractures and a linear skull fracture occurred during the application of the maximum head force of 4350 lb. The chest target was 6 in. in diameter with 15/16 in.of padding. The padding was rolled over the edge of the target to minimize localized high force areas on the ribs. A 1/8 in. diameter rod was inserted through the chest and fastened through a ball joint and flange to the soft tissue at the sternum.

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.

A new laminated automobile windshield called Triplex “Ten-Twenty,” fabricated from two thermally stressed glass plies of 2.3 mm soda-lime float glass laminated with a 0.76 mm HPR polyvinyl butyral interlayer, has been biomechanically evaluated by Triplex Safety Glass Co., Ltd., using a dropping headform and a skull impactor, and by Wayne State University, using a 50th percentile anthropomorphic dummy on the WHAM III sled test facility. The results of these evaluations at velocities up to 60 km/h are expressed in terms of Gadd index, head injury criterion, and various laceration scales including the new Triplex laceration index (TLI). Some details are also given of other properties of the windshield. The results of the evaluations indicate that the Ten-Twenty windshield offers a reduction of about two units on the TLI scale equivalent to one of the following: 1. A 99% reduction in the number of cuts when the length and depth of cuts remain unaltered. 2.

Knee impacts along the femoral axis of unembalmed male cadavers and Part 572 dummies were made with rigid pendulum impactors at Wayne State University. The dummy exhibited significantly higher knee impact forces than the cadaver subjects. This difference of response is shown to be due to differences of effective leg mass and knee padding. The dummy with its heavy rigid metal skeleton is not like its human counterpart, where the majority of the leg weight is composed of loosely coupled flesh. The knee impacts of the dummy subjects showed that the dummy femur transducer force was consistently less than the corresponding dummy knee impact force by a constant ratio of 0.8. We recommend that the “skeletal” weight of the Part 572 dummy leg should be substantially reduced, with the weight difference being added to a properly simulated leg flesh. Also, the simulated flesh covering of the knee should be modified to reduce the peak force resulting from rigid body impacts.

An improved windshield with a special, thin, plastic inner surface attached to the inner surface of a three layer windshield similar to those used in the United States minimizes lacerations from occupant impact to the windshield during a collision. The plastic coats the sharp edges of the broken glass preventing or minimizing laceration. It was evaluated by comparing its laceration performance with that of a standard windshield in simulated barrier crashes at velocities up to 65 km/h. No lacerations resulted from impact to the Securiflex windshield at Barrier Equivalent Velocities up to 65 km/h. Substantial laceration resulted at velocities above 20 km/h with the standard windshield. It is concluded that the Securiflex windshield essentially eliminates lacerations in the particular vehicle involved at velocities up to at least 65 km/h.

Children riding on the bed over the cab in campers can be injured in forward force collisions from striking the glazing material and/or being ejected through the opening. The two types of glazing commonly used are acrylic and laminated. A comparison of the performance of the two types of glazing in simulated forward force collisions at velocities up to 30 mph showed the acrylic material to pose threats of neck and back injury and the laminated material to result in lacerations. Ejections occurred with the acrylic that were not present with the laminated windshields when correct glazing techniques were used. With poor installation procedures, ejections occurred in both types of glazing materials. It is concluded that the best way to avoid injury is to prevent the child from riding in the over-the-cab bunk. If the child does ride there, his body axis should be positioned at an angle to the longitudinal axis of the vehicle.

Though the steering wheel has been maligned as a primary cause of injuries in automobile collisions, studies show it is the first passive restraint system in the automobile. Adding an airbag to the steering wheel distributes the energy load better than the wheel alone, and the airbag takes advantage of the space between occupant and steering wheel to protect the driver further. Specifically, the airbag utilizes space to decelerate the occupant, prevents concentrated loads on the torso, stops the face from hitting the steering wheel rim, and helps distribute impact load over a larger area. The airbag has three major components-the sensor, inflator, and airbag. The functioning of these components, as well as experimental investigations conducted to determine operational capabilities of the system, are discussed.

The paper gives an evaluation of the performance of lap and shoulder belt restraint systems currently being used in American-built automobiles. Comparisons are made of the response characteristics of a volunteer, an anthropometric dummy, and a cadaver when subjected to identical collision environments while wearing a three or four point torso restraint system as occupants of the right front seat. Simulated frontal force barrier collisions in a modified automobile provided the realistic environment for the restraint system performance study. Human tolerances, interior vehicle geometry, and the interaction of the restrained occupant with the vehicle during the collision are reported in detail.

Human volunteers were subjected to static and dynamic environments which produced noninjurious neck responses for neck extension and flexion. Cadavers were used to extend this data into the injury region. Analysis of the data from volunteer and cadaver experiments indicates that equivalent moment at the occipital condyles is the critical injury parameter in extension and in flexion. Static voluntary levels of 17.5 ft lb in extension and 26 ft lb in flexion were attained. A maximum dynamic value of 35 ft lb in extension was reached without injury. In hyperflexion, the chin-chest reaction changes the loading condition at the occipital condyles which resulted in a maximum equivalent moment of 65 ft lb without injury. Noninjurious neck shear and axial forces of 190 lb and 250 lb are recommended based on the static strength data obtained on the volunteers. Neck response envelopes for performance of mechanical necks are given for the extension and flexion modes of the neck.

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.