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In 2012, the Insurance Institute for Highway Safety (IIHS) began a 64 km/h small overlap frontal crash test consumer information test program. Thirteen automakers already have redesigned models to improve test performance. One or more distinct strategies are evident in these redesigns: reinforcement of the occupant compartment, use of energy-absorbing fender structures, and the addition of engagement structures to induce vehicle lateral translation. Each strategy influences vehicle kinematics, posing additional challenges for the restraint systems. The objective of this two-part study was to examine how vehicles were modified to improve small overlap test performance and then to examine how these modifications affect dummy response and restraint system performance. Among eight models tested before and after design changes, occupant compartment intrusion reductions ranged from 6 cm to 45 cm, with the highest reductions observed in models with the largest number of modifications.

The Insurance Institute for Highway Safety (IIHS) is investigating small overlap crash test procedures for a possible consumer information program. Analysis of real-world small overlap crashes found a strong relationship between serious head and chest injuries and occupant compartment intrusion. The main sources of serious head injuries were from the A-pillar, dash panel, or door structure, suggesting head trajectories forward and outboard possibly bypassing the airbag. Chest injuries mainly were from steering wheel intrusion and seat belt loading. In developing this program, two test dummies were evaluated for predicting occupant injury risk: midsize male Hybrid III and THOR. In the collinear small overlap crash tests conducted here, results from the two dummies were similar. Both predicted a low risk of injury to the head and chest and sometimes a high risk of injury to the lower extremities. Head and torso kinematics also were similar between dummies.

Anthropometric test devices (ATDs) instrumented with potentiometers and accelerometers are used regularly to assess thoracic injury risk in side impact crash tests. Measurements from these sensors are compared with injury assessment reference values (IARVs) for lateral loading to establish the risk of injury for humans subjected to similar impacts. In crash tests, the deflections and deflection rates derived from these two types of sensors (potentiometers vs. accelerometers) have varying degrees of agreement. In some cases, differences can be relatively large. In the past, it was unclear whether the reason for the differences was off-axis loading that misaligned the accelerometers used in the calculation, an inherent inability of the potentiometer to capture high deflection rates under certain conditions, or some other phenomenon.

Excessive movement of steering columns in crashes can significantly degrade the performance of restraints, especially airbags. Although steering column movement does not appear to be a major problem in full-width rigid barrier crashes, it can be an issue in other frontal crash types. Results from 106 frontal offset crash tests at 64 km/h (40 mi/h) were used to characterize different patterns of steering column intrusion for different vehicle types. Large movements of the steering column often were associated with the dummy’s head striking the steering wheel through the airbag. Some of the tested models were redesigned over the course of this testing, and comparisons with older designs showed that improving the structural integrity of the occupant compartment could lead to less longitudinal movement of the steering column, but this was not necessarily the case for vertical column movements for some models in the data set.

The knee and ankle joint pivots of the Hybrid III dummy's leg are positioned in approximately the same orientation as the knee and ankle joint rotation centers of a human in a normal driving posture. However, the dummy's leg assembly is not simply a straight member between these two pivots. It is a zigzag-shaped solid link composed of one long straight section in the middle and short angled sections at either end, which form the pivots. The upper and lower tibia load cells are mounted on the straight middle section, making the upper tibia load cell location anterior to the line between the ankle and knee pivots and the lower tibia load cell location slightly posterior to the line between the pivots. Hence, an approximately vertical force on the foot can act along the line behind the upper tibia load cell and in front of the lower tibia load cell, creating bending moments.

This study, which is an extension of an earlier study, examined an additional 64 frontal crashes of airbag-equipped vehicles in the 1997-98 National Automotive Sampling System Crashworthiness Data System (NASS/CDS) in which the driver died. The principal cause of death in each case was determined based on an examination of the publicly available case materials, which primarily consisted of the crash narrative, the injury/source summary, and photographs of the crashed vehicle. Results were consistent with the earlier analyses of the 1990-96 NASS/CDS files. In the combined data set (1990-98), gross deformation of the occupant compartment was the leading cause (42 percent) of driver deaths in these 116 frontal crashes. The force of the deploying airbag (16 percent) and ejection from the vehicle (13 percent) also accounted for significant portions of the driver deaths in these frontal crashes. There continues to be little or no evidence that airbags deploy with too little energy.

A BioRID (biofidelic rear impact dummy) representing a 50th percentile adult male was seated in the front passenger seat of six new vehicle models in a series of low-speed crash tests. The neck injury criterion (NIC) and other dummy responses that may indicate whiplash injury risk were recorded. Both front-into- rear and rear-into-barrier tests with an average velocity change of 11 km/h were conducted. Head restraints were tested in both adjusted (up) and unadjusted (down) positions. Damage to all models was minor, and longitudinal vehicle accelerations were low (less than 7 g). Neck extension angles and bending moments were much less than injury assessment reference values (IARV) (80 degrees and 57 Nm, respectively), indicating low risk of hyperextension injuries. Neck tension and transverse forces also were less than IARVs used to indicate the risk of more serious neck injuries.

Lower extremity injuries resulting from motor vehicle crashes are both frequent and associated with considerable long-term impairment. Deformation of a vehicle's occupant compartment resulting in intrusion into the foot area is often cited as a source of many of these injuries. Similarly, collisions involving only a portion of a vehicle's front structure are typically said to produce greater intrusion than fully engaged crashes. The relationship between occupant compartment intrusion and the risk of lower extremity injuries was examined through a series of offset frontal crash tests of 1984-89 Oldsmobile Cieras. Results from both car-to-car and car-to-barrier test crashes with instrumented dummies confirm that there is a relationship between occupant compartment deformation and the loads acting on the lower extremities of vehicle occupants, even when crash severity has been controlled.

Since 1978, the National Highway Traffic Safety Administration (NHTSA) has been testing the frontal crash protection provided by new cars in the United States. In the New Car Assessment Program (NCAP), vehicles are crashed into a stationary, full width, rigid barrier at 35 mi/h (56 km/h). Occupant protection is measured by comparing accelerations, forces, and deflections experienced by the head, chest, and upper legs of 50th percentile male Hybrid II or III anthropometric dummies restrained in the driver and right front seat passenger positions. The procedures are similar to those specified in Federal Motor Vehicle Safety Standard 208, except that the speed is 5 mi/h faster resulting in a test that requires the car to manage 36 percent more energy.