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Frontal-Impact Crash Tests

Frontal-Impact Crash Tests

By Jeff Youngs, February 24, 2012
The National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) are the only two organizations that conduct crash tests in the United States. While both organizations conduct frontal- and side-impact tests, each organization conducts its tests quite differently. As a result, ratings from both organizations can be useful when shopping for a new vehicle.

The NHTSA test
In the NHTSA test, two crash-test dummies the size of an average adult male (5 feet 7 inches tall and 170 pounds) are placed in the driver and front passenger seats of the test vehicle and secured with seat belts. The vehicle is then crashed head-on into a fixed barrier at 35 mph, which is the equivalent of two vehicles of similar weight hitting each other head-on at that same speed. The force of the impact on the dummies is measured, and NHTSA gives the vehicle a star rating (from one to five stars) based on the percent chance of serious injury to the head and chest (which means that the injury requires immediate hospitalization and may be life threatening). NHTSA's star ratings range from one star (46 percent or greater chance of serious injury) to five stars (10 percent or less chance of serious injury).

The IIHS test
In the IIHS test, a single crash-test dummy the size of an average adult male is placed in the driver's seat of the test vehicle and secured with the seat belt. Measurements of impact force are taken from the head, neck, chest, legs, and feet to determine the likelihood of injury in any of those areas.

The frontal test that IIHS conducts is an offset test, meaning that only one side of the vehicle's front end is crashed. IIHS uses this type of test because the agency feels that it is more common in real-world frontal collisions for a vehicle to be impacted at an angle when most drivers turn in an attempt to avoid the collision. In the IIHS test, the vehicle strikes a deformable barrier on the driver's side at 40 miles per hour. Approximately 40 percent of the front of the vehicle is impacted.

IIHS grades the vehicles it tests, assigning one of four ratings: good, acceptable, marginal, or poor. Ratings do not correlate to a percent chance of injury (as in the government's test) because IIHS not only assesses occupant injury, but also how well the vehicle structure performs, in addition to the movement of the dummy, such as a partial ejection from the vehicle.

Interpreting the results
While it would seem at first glance that the two tests are measuring basically the same thing, the fact that the tests are conducted differently means that the results tend to be quite different. Today's vehicles are designed so that the energy created in a collision is dispersed through the body of the vehicle and away from the occupants. This is done quite successfully in most vehicles when they are hit head-on, but this also means that, in a head-on collision, the force placed on the restraints to hold the passengers in place is much greater.

It's important to note that both tests can only be used to get an idea of how the vehicle would perform in a collision with a vehicle of similar size and weight or in a single-vehicle collision. They cannot be used to assess how a vehicle would fare if it collides with a vehicle that is significantly different in size.To view crash-test results from both organizations, visit NHTSA's (www.safercar.gov) or IIHS' (www.hwysafety.org) Web site.
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