St John's Transportation & Cars Research - Crash Tests- What You Need to Know

Although 2003 had the lowest crash fatality rate per 100 million miles of travel on record, there were still 42,643 people killed and nearly 2.9 million people injured on U.S. roads, according to the National Highway Traffic Safety Administration. Because of this, understanding how a vehicle performs when involved in a crash is important to consider before making a purchase.

Crash Tests (How Stuff Works)

More on Crash Tests

One governmental agency and one nonprofit trade group conduct consumer testing of cars:

They crash-test vehicles to measure damage to vehicle occupants and cost to repair, and recently they have begin testing rollover safety. All vehicles sold in the United States must pass Federal Motor Vehicle Safety Standards in the form of 30-mph frontal and 33.5-mph side-impact compliance crash tests, but the relative safety of all vehicles above this minimum standard varies greatly. A vehicle's center of gravity and overall width are the primary factors in determining its rollover rating.

Not All Results Can Be Compared

Model-to-model comparisons of frontal crash-test ratings enable comparisons within a vehicle class or between models of comparable weight (within 250 pounds). If there is a collision with a larger or smaller vehicle (or a lower- or higher-riding vehicle), the heavier vehicle would protect its occupants better than a lighter one (if all other factors were equal). This means that a larger vehicle with a Poor rating is not necessarily safer than a smaller vehicle with a Good rating. Side-impact crash tests are comparable across classes because the sled that rams the test vehicles has a consistent size and weight for all tests.

Crash Tests Differ by Agency

The two testing agencies perform different types of frontal tests.

Other organizations around the world conducting crash tests (though with different parameters and protocols than the US, so comparisons should be made with caution):

Side-Impact Ratings Deficiencies

Side-impact crash tests done by NHTSA cover a larger number of car models than IIHS for side-impact protection, but are arguably flawed for two reasons:

The IIHS side-impact test measures head injury as well, and employs a sled as high and heavy as a full-size SUV or pickup, the more dangerous scenario. Unfortunately, IIHS has only recently begun this program and few models have been tested. Again, because the sled used has a consistent size and weight for all tests, comparisons of side-impact ratings are valid across vehicle classes.

Rollover Ratings Imperfect but Improving

NHTSA's original Rollover Resistance Ratings were begun in the 2001 model year, but rated a model's rollover propensity based solely on a mathematical calculation of the vehicle's center of gravity, and without a full passenger or cargo load (which typically raises a vehicle's centre of gravity). Since the 2004 model year, the NHTSA has combined this calculation with a "fishhook" dynamic driving test in which the test vehicle swerves suddenly and then overcorrects. The combined results, called simply NHTSA Rollover Ratings, give a percentage chance of rollover, based on whether or not the model tipped up on two wheels during the fishhook test. Some automakers now criticize them for extrapolating some conclusions.

Some Models Are Not Rated

Both agencies concentrate on the highest-volume vehicles (and both agencies purchase their test subjects from dealerships, just as consumers do), so convertibles are rarely tested, and results for new or recently re-engineered models unlikely to appear until months after the vehicle goes on sale. NHTSA will typically indicate that a vehicle is TBT (to be tested), or that results are pending, or under review, though IIHS gives no indication of future reports. If the model you seek is missing, results may be pending or the vehicle may not be eligible.

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