A study was conducted by selecting cases from available NCSS/NASS data on nearside crashes involving fatal chest and abdominal injury. Twenty-five cases indicated over-involvement of older front-seat occupants in multi-vehicle side impact crashes (76%>50 years old and 28%>70 years old). Analysis of the 1975-86 FARS confirmed that older occupants are overrepresented in nearside crashes with an incidence of 64%>50 years old and 36%>70 years (as compared to 26%>50 and 8%>70 respectively for single vehicle frontal crashes). The 1982-1986 NASS indicate that 42% of the seriously injured front seat occupants over 40 years old were in nearside multivehicle crashes. This is nearly twice the proportion for younger occupants.

The individual case study also showed that 88% of the multi-vehicle nearside crashes were at intersections and that the driver of the struck vehicle frequently caused the crash by driving error (52%) or traffic violation (17%). The majority of the cases occurred in daylight hours and on dry roads. Alcohol use was not a factor. Changes in visual perception, judgment and attention in the older driver may be factors in crash causation. In addition, a reduced tolerance to impact force probably contributes to injury causation. In terms of automotive design, improvements in side interior padding should aim at safety of older occupants because of their high involvement in this crash type. The analysis raises further questions about the validity of the NHTSA proposed test dummy and injury criterion (SID and TTI) because the dummy develops high, nonhuman-like forces and the injury criterion is sensitive to both protective and unprotective padding. The combination would lead to stiff interiors that particularly place older occupants at continued risk in a nearside crash.

Although an analysis of photographs from the sideimpact vehicles indicated that 44% of the crashes had side-structure deformation that was similar to that produced in the NHTSA moving deformable barrier test, only 24%-32% of the cases actually addressed the proposed dynamic test. The results of this analysis bear on the preliminary regulatory impact analysis of cost benefit in conducting the side-impact dynamic test. In addition, the review supports the concept that improvements in side-impact protection may be better realized by a slower crash test so that softer padding can be designed to reduce the injury risks of older occupants. The development of improved side interior padding further hinges on the use of a human-like crash dummy and a valid injury criterion, such as the Viscous response, that is sensitive to the underlying risks of internal organ and soft tissue injury of occupants.