Clyde C. Culver

Involvement of older drivers in multivehicle side-impact crashes

Side impacts were studied using three separate analyses. National Accident Sampling System (NASS) and National Crash Severity Study (NCSS) cases were reviewed on multivehicle crashes involving fatal chest and abdominal injury by interior contact. Twenty-five cases were analyzed and showed an unusually high involvement of older occupants. Analyses of the 1975-1986 FARS confirmed an overinvolvement. Sixty-four percent of near-side seated occupants were over 50 years old and 36% over 70 in fatal multivehicle side impacts. In contrast, 26% of victims in single-vehicle frontal crashes were over 50 and 8% over 70 years old. Analysis of the 1982-1986 NASS showed that single-vehicle side impacts are not an important injury risk for older drivers, except on icy or wet roads. In contrast, the risk of injury in multivehicle side impacts increases steadily with age and is a major problem for older drivers. The individual NASS and NCSS cases also showed that 88% of the multivehicle side crashes took place at an intersection and that the driver of the struck vehicle frequently caused the crash by driving error (48%) or traffic violation (16%). The majority of cases occurred in daylight hours, on dry roads, and without alcohol involvement. Changes in visual perception, judgment and attention of the older driver may be factors in their missing a traffic signal or turning in front of traffic under the right-of-way. In addition, a reduced tolerance to impact force probably contributes to the injury. Although an analysis of photographs of the side-impacted vehicle indicated that 44% had side-structure deformation that was similar to that produced in the National Highway Traffic Safety Administration (NHTSA) moving deformable barrier test, only 24%-32% of the cases actually addressed the proposed NHTSA dynamic side-impact test. The results of this analysis bear on the agencys preliminary regulatory impact analysis.

Bolster impacts to the knee and tibia of human cadavers and an anthropomorphic dummy

Knee bolsters on the lower instrument panel have been designed to control occupant kinematics during sudden deceleration. However, a wide variability in car occupant anthropometry and choice of seating posture indicates that lower-extremity contacts with the impingement bolster could predominantly load the flexed leg through the knee (acting through the femur) or through the tibia (acting through the knee joint). Potential injuries associated with these types of primary loading may vary significantly and an understanding of potential trauma mechanisms is important for proper occupant restraint. Impacts of the bolster panel against the knee or lower leg were simulated in 10 human cadaver and anthropomorphic dummy tests and the following aspects were assessed: (1) biomechanical response for lower-extremity impacts, (2) potential mechanisms of skeletal and ligamentous trauma, (3) differences between human cadavers and an anthropomorphic test dummy response, and (4) knee-joint ligament failure characteristics in isolated knee-joint tests. For the covering abstract see IRRD 810752. (TRRL)

A Study of Driver Interactions with an Inflating Air Cushion

Conceptually, a steering wheel mounted air cushion is inflated before the upper torso of the driver significantly interacts with the cushion. However, this might not be the case for some seating postures or vehicle crash environments which could cause the driver to significantly interact with an inflating cushion. These experiments utilized several environments to study the interaction between an inflating driver air cushion and mechanical surrogates. In these laboratory environments, the measured responses of mechanical surrogates increased with diminishing distance between the surrogates sternum and the steering wheel mounted air cushion. For the covering abstract see IRRD 810752. (Author/TRRL)

Anthropometry of Seated Women during Pregnancy: Defining a Fetal Region for Crash Protection Research

An anthropometric description was developed for the fetal region of women at three, six, and nine months of pregnancy. This involved superimposing a fetal ellipse on abdominal and pelvic ellipses of seated women from a previous study. The data were developed for women of 5th, 50th, and 95th percentile size. The ellipses identify body contact zones on the side and front which would interact with the fetal region in a crash. The new information provides spatial characteristics of pregnant women for the development of test dummies, accommodating restraints, and friendly interiors and for enhancing crash protection. This research addresses the 342 deaths of pregnant women estimated to occur annually in motor vehicle crashes.

THE ROLE OF STEERING WHEEL STRUCTURE IN THE PERFORMANCE OF ENERGY ABSORBING STEERING SYSTEMS

This study identifies important parameters that influence the basic response mechanics of a compressible column steering assembly. Energy can be absorbed either by column compression and/or steering wheel deformation, depending on relative deformation force. Neither column compressive force nor steering wheel deformation force are uniquely defined but depend on several parameters. Steering wheel deformation force is dependent on occupant load distribution. The force necessary to compress the column differs from the column EA element compressive force due to inertial and geometric considerations. For our test conditions and the components we studied, off axis impact resulted in initial steering wheel deformation with the wheel and column sharing energy absorption. Axial impact resulted in almost negligible wheel deformation and the column was the energy absorbing component. For the covering abstract of the conference see HS-036 716. (Author/TRRL)

TEST DUMMY INTERACTION WITH A SHOULDER OR LAP BELT

Belt interaction with the dummys chest or pelvis was investigated during simulated frontal decelerations to develop a better understanding of the mechanics of belt restraint. Hyge sled tests were conducted at acceleration levels of 6-16 gs with a Part 572 dummy forward facing on an automotive bucket seat. Dynamics were compared in similar tests where the dummy was restrained by a conventional shoulder belt or belt segments attached to a modified sternum -- a steel sternum with extensions for fixed belt attachments. Tests were also conducted with a conventional lap belt or belt segments fixed to an extension of the H point. Deformation characteristics of the standard and modified thorax were determined for a lateral and superior point load or a belt yoke compression of the sternum. The pelvic structure was also compressed by a lap belt.

Performance of a shoulder belt and knee restraint in barrier crash simulations

Simulated frontal barrier crash experiments were conducted with unembalmed human cadavers and an anthropomorphic dummy restrained by a two-point shoulder belt. In the first test, an experimental bolster was specifically positioned so that the cadavers lower leg would strike the bolster, thus inducing restraining loads entirely below the knee joint. The analysis of occupant kinematics showed that the flexed knee rode over and forward of the low-positioned bolster. Restraint induced considerable shearing load across the knee joint. Factors influencing the performance of a shoulder belt and knee restraint system were studied in the remaining experiments. Positioning the bolster to provide full knee contact and early femoral loading, and orienting the bolster face to reduce knee joint shear loads were identified as important parameters for improved performance of the knee restraint in these tests. Language: en

Occupant seating anthropometry: body ellipses and contact zones for side-impact protection research

Abstract The study has developed an anthropometric description of seated occupants and determined body regions representing major paths in side-impact crashes. The study has identified five major body ellipses defining the head, shoulder, chest, abdomen and pelvis of seated occupants of various sizes, including the six-year-old child. Body contact zones have been determined for front-seated occupants. These templates provide information for the design of side interiors to improve occupant protection in side-impact crashes by load-transfer and energy-absorption characteristics of biocompatible interiors.

FACTORS INFLUENCING KNEE RESTRAINT

A planar mathematical model was developed to provide means of studying factors which can influence the function of lower torso restraint via a padded lower instrument panel or knee bolster. The following factors were judged to play the most significant role: (1) initial fore-and-aft position of the seated occupant relative to the knee restraint; (2) location of the knee-to-bolster contact; (3) angular orientation of the bolster face; (4) primary axis of the bolster resisting force, (5) variations in vehicle crash parameters; and (6) deformation characteristics of the bolster. The model of a seated occupant included radiographic and empirical data on the anatomy of the links and joints in the lower extremity. Emphasis was also placed on determining a range of reference location, orientation, and primary axis of resistance of the knee bolster so that an effective restraint may be provided for the 5th percentile female, 50th percentile male, and 95th percentile male occupant.

Significance of Head-to-Knee impacts—A Comparison of Dummy and Cadaver Responses

Head-to-knee interaction of the right front passenger dummy can occur in some 30-35 MPH crash barrier tests. The biofidelity and significance of these interactions as related to predicting human response is addressed. In a series of laboratory experiments an instrumented headform was dropped on the dummy knee to simulate the barrier interactions. These test results were then related to the human by dropping the same headform on the cadaver leg. Head-to-knee impact tests on cadaver subjects indicate a lack of biofidelity in the dummy lower leg structure for this type of impact. Assuming that head-to-knee interaction actually occurs in field accidents, values of HIC measured from dummy crash simulation experiments are likely to overestimate the severity of the interaction.