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The objective of this analysis is to evaluate the effectiveness of restraints in preventing injury-producing contacts of specific body regions, such as the head or chest, with specific interior components. In order to make comparisons by restraint use, an injury rate is calculated as the number of injury-producing contacts per hundred involved occupants. Data, including the Occupant Injury Classification (OIC), are from the 1988-92 National Accident Sampling System (NASS) Crashworthiness Data System (CDS). The analysis presented is limited to passenger vehicle drivers in towaway, frontal impacts. Injury-producing contact rates are compared for four restraint configurations: unrestrained, three-point belted, driver airbag alone, and driver airbag plus three-point belt. For each restraint configuration, contact rates are compared by three categories of injury severity, AIS 1, AIS 2, and AIS 3-6, body region injured, and contact area producing the injury.

Rollover and ejection are associated with heavy-truck occupant fatalities almost twice as frequently as with passenger-car occupant fatalities. A panel reviewed 41 in-depth cases to assess the possible effectiveness of restraint use and the contribution of rollover and ejection to the fatal injuries. The panel's responses indicated that belt use was expected to be particularly effective in preventing fatalities resulting from occupant ejection. A review of the proportion of ejections by model year indicated that 1972 model year and newer heavy trucks have about 20 percent fewer ejections than pre-1972 heavy trucks. Ejection through the doors was reduced by 80 percent. This difference seems to reflect the effectiveness of FMVSS 206, which required stronger door latches.

The relationship between crash severity and injury level is illustrated using the Restraint System Evaluation Study (RSES) data and Texas police-reported data. The RSES data are used to demonstrate that the probability of an injury (or fatality) is a function of both (a) the risk of injury, given a set of crash factors, and (b) crash exposure, or the chance of those factors occurring. The Texas data are used to demonstrate that crash exposure can change with time. Changes in crash exposure can alter the distribution of injuries (or fatalities) independently of motor vehicle standards or design. Texas and CPIR data are used to demonstrate that the risk of fatality is associated with many crash factors other than the traditional speed-related measures.

For the 1997 data year, UMTRI's Center for National Truck Statistics collected data on rear underride as part of its Trucks Involved in Fatal Accidents (TIFA) survey. Data collected included whether the truck had a rear underride guard, whether the striking vehicle underrode the truck, and how much underride occurred. A primary goal was to evaluate rear underride of straight trucks. Overall, 453 medium and heavy trucks were struck in the rear by a nontruck vehicle in a fatal crash in 1997. Some underride occurred in at least 272 (60.0%) of the rear-end crashes. For straight trucks, there was some underride in 77 (52.0%) of the crashes, no underride occurred in 43 (29.1%) of the fatal rear-end crashes, and underride could not be determined in the remaining 28 (18.9%) straight truck rear-end crashes. Despite the fact that three-fourths of tractor combinations had an underride guard on the trailer, underride was more common for tractor combinations.