Understanding Crash Test Ratings

By Zac Estrada
Last Updated 05/12/2015

Stars, Top Picks, “Good.” There are numerous ratings automakers throw around for crash-test ratings to basically say their cars are safe. The tests those scores actually correlate to are what’s important for consumers.

Here’s a rundown of the two main crash-testing firms in the U.S. and what they test.

Crash Test Agencies

The National Highway Traffic Safety Administration (NHTSA) conducts crash tests for new models sold in the U.S. since 1978. They give star ratings for test results, from 1-5 stars. Since 1997, side impact crash results have been part of evaluation. And since 2011, cars are given an overall vehicle score for crash protection in all of the tests.

Then there’s the Insurance Institute for Highway Safety (IIHS). It’s a non-profit organization funded by insurance companies and insurance associations. IIHS ratings are largely derived from Good, Acceptable, Marginal and Poor results in each of its tests. Models that do well in all of their tests are typically awarded as “Top Safety Picks,” and the very best get “Top Safety Pick +” honors.

Both agencies generally base scores on crash forces toward a dummy’s head, neck, chest, pelvis, legs and feet, representing the likelihood and severity of injuries were these humans in an actual crash.

Front Crash Tests

NHTSA bases their frontal crash scores on a 35-mph collision into a flat barrier meant to represent a car of similar size and weight. According to the administration, dummies representing “an average-sized adult male and a small-sized adult female are placed in the driver and front passenger seats.”

IIHS is noted for using an offset front crash test at 40 mph. Whereas the entire front of the car takes the impact in the NHTSA test, the IIHS says its test uses just 40 percent of the frontal area of the vehicle. As with the government, IIHS crashes its cars into barriers that represent a similarly sized vehicle.

Small-Overlap Crash Tests

In 2012, the IIHS introduced what it calls the small overlap frontal test. The 40-mph offset impact is confined to the vehicle’s left-most edges, which the agency says simulates hitting a tree or pole or clipping another car. It’s significant because most of the areas that absorb impact on the front of the car tend to be more centrally located. Since the IIHS began this test, many designs have been unable to score well in it without modification. Automakers are generally designing new models to perform well in this test.

Side Impact Crash Tests

Both NHTSA and IIHS evaluate side impacts to new vehicles, using a dummy mounted in the front and rear seat, if applicable. NHTSA uses a 3,015-pound barrier moving at 38.5 mph that crashes into the stationary vehicle.

NHTSA additionally performs a side impact pole test, where a smaller, adult female dummy is put in the driver’s seat. The vehicle is then pulled sideways at 20 mph into a pole that’s meant to represent a tree and tests the strengths of the pillars and roof of the car.

IIHS uses a taller, 3,300-pound. barrier to represent an SUV or truck slamming into the side of a stationary car. Dummies representing an average-sized woman and a 12-year-old child are placed in the front and rear seats, respectively.

Rollover and Roof-Strength Tests

Stemming from the increased popularity of SUVs and light trucks, and well-documented cases of those types of vehicles, NHTSA introduced a rollover resistance rating in 2001. Five-star cars have a 10 percent or less chance of rollover. Crossovers and SUVs typically achieve no more than four stars in this study.

IIHS performs a roof-strength test. A “Good” rating is for a car that can support a force at least four times the weight of the vehicle. A “Poor” rating is anything less than 2.5 times the weight of the car. Current federal legislation requires every new car sold in the U.S. be able to support at least 1.5 times the weight of the car, before occupants or cargo is added.

Advanced Safety Tech

In the wake of more cars offering sophisticated crash prevention or mitigation features, IIHS began testing vehicles with systems such as automatic braking and forward collision alert. To get the top “Superior” rating in this evaluation, a car must be able to prevent a crash at speeds of 12 mph and avoid (as much as possible) an impact at up to 25 mph.