Crashworthiness is a measure of how well a vehicle performs during a collision. The crashworthiness of a vehicle is not simply how little damage it experiences, but how well it holds up to its intended design. Crashworthiness in highway vehicles can be divided into two categories: the effectiveness of the vehicle structure, and the effectiveness of the safety components within the vehicle.
Behavior of Automobile Structures in a Collision
When a car strikes another object, such as another vehicle or a telephone pole, the car is subjected to a rapid deceleration. Some of the energy is absorbed by the car, and some is absorbed by the other object. A collision is generally a combination of a plastic collision, where all energy is absorbed by the two colliding objects, which then come to rest, and an elastic collision, where all energy is transmitted through the two objects, forcing them to bounce back in different directions (think of billiard balls).
In older vehicle designs the frame structures were very stiff, and relatively little deformation of the structure occurred in accidents. The problem, in this case, is that the occupants, being not integral to the car structure, would be thrown forward in a frontal collision, impacting the steering column, dashboard, and/or the windshield. In addition to external injuries, the deceleration that occurs when a person strikes the interior of the vehicle could potentially cause brain damage. However, the damage to the vehicle was generally minor, except in the most violent collisions.
Advances in Automobile Crashworthiness
Over time, advances in vehicle safety mechanisms have reduced the severity of injuries sustained in vehicle collisions. Some of these advances include:
- Seatbelts, which prevent occupants from being thrown forward during a frontal collision.
- Headrests, which prevent whiplash, or a hyperextension of the neck, during a rear collision.
- Crumple zones, which are designed to absorb energy during a collision by collapsing, effectively reducing the degree of deceleration experienced by the occupants
- Airbags, which prevent occupants from impacting interior structures of the vehicle during a collision and reducing the deceleration of the occupants.
- Side impact zones, which include airbags to cushion lateral deceleration and improved frame construction to prevent penetration into the vehicle cabin.
Because of the inclusion of these vehicle safety mechanisms, it is common for automobiles to sustain significant damage during a collision. This damage, combined with the relatively high expense of replacing airbags, causes many vehicles to be considered totaled after an accident, since the repairs would cost more than the car is worth.
Research in Automobile Crashworthiness
he National Highway Traffic and Safety Administration (NHTSA), which is part of the Department of Transportation (DOT) is charged with reducing the number of deaths and injuries on America’s highways. NHTSA sponsors research in a wide variety of programs, including airbag design and deployment, seatbelts, child safety seats, and the effectivness of crumple zones.
The Insurance Institute for Highway Safety (IIHS) is an independent non-profit organization funded by insurance companies. It’s mission is to reduce the number of highway injuries and fatalities through research and testing. IIHS is most well-known for its crash testing and crash rating for vehicles. The institute purchases vehicles of all makes and models and subjects them to varying collision scenarios, then publishes a crash rating for each vehicle. Consumers often use the IIHS rating as a factor when purchasing a vehicle.
Automobiles have experienced a dramatic improvement in occupant safety since the automobile was developed over a century ago. Understanding the behavior of vehicles in collisions and designing safety mechanisms into new vehicles have dramatically reduced the degree of injury and the frequency of death in automobile accidents.