• From an engineering perspective, crashworthiness is the ability of the vehicle to prevent occupant injuries in the event of an accident. This topic is then the technical foundation for the legal doctrine of crashworthiness or enhanced injury theory. It should be noted here that the accident is a given when assessing the crashworthiness of a vehicle. It is further worth noting that the cause of the accident is technically irrelevant in crashworthiness cases even if the severity of the accident is an issue. Severity can be assessed independently of the cause of the accident. Severity is recorded in steel- in sheet metal damage for the most part. Preceding instances of human agency and even mechanical failures that produced the record are not relevant for interpreting it. If accident causation is an issue in a crashworthiness case, it is for legal reasons then and not technical ones. (Various courts have in fact upheld the view that driver error or malfeasance is irrelevant in crashworthiness cases.)

• The questions of vehicle crashworthiness are then: Given the injury mechanisms of an accident, and typically some measure of its severity (see delta v ) could the occupants of the vehicle have fared better than they did? Was there some feature lacking in the vehicle which would have reduced their injuries and should have been there on some theory or other?

• Crashworthiness is not the same as vehicle safety, and the two topics must be distinguished. The safety afforded by a vehicle depends both on crashworthiness and accident avoidance features, the latter including such things as ABS, good handling characteristics, or even oversize tires. These two concepts are frequently confused to the detriment of those raising the crashworthiness issue. One vehicle might be safer statistically than another and still have a significant crashworthiness defect. It could even conceivably be less crashworthy overall while still being a "safer" vehicle. This is because vehicle crashworthiness depends on designed in features as well as equipment specifications which can be viewed as design features. A given vehicle either has these features or it doesn't regardless of its accident or even injury rates.

• A typical list of crashworthiness features includes things like air bags, seat belts, crumple zones, side impact protection, interior padding and head rests. These features may or may not be present in a particular vehicle and may or may not work even if present. All of these items have been available since the early 1970's, yet many are still not found in vehicles produced in the 1990's. Some are mandated by FMVSS (CFR 49: 571.201pp.) to one degree or another. Gradually these standards are being upgraded to include all of the items listed above as well as other features long known to be required for occupant safety.

• The features list for crashworthy vehicles is generated by consideration of the fundamental accident modalities to which all highway vehicles must be assumed to be subject. These are the "foreseeable" accident types: impacts at any angle on all vertical surfaces of the vehicle (front, rear, left and right sides) as well as rollover accidents. Crashworthiness features must minimize second collision (occupant into vehicle interior) forces and prevent ejection and reduce fire risk.

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