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Crash-Test Safety Ratings, Explained

Crash Test Ratings Explained

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Crash-test ratings are referenced often, but what do they really mean?

Ever wonder how well a particular car or truck would fare in a crash? The safest way to find out is to check its scores in the crash tests conducted by the government and the insurance industry.

But before you take the ratings at face value, it's important to understand how they're derived.

Crash-test results are reported by the government's National Highway Traffic Safety Administration at nhtsa.gov/ratings, and by the Insurance Institute for Highway Safety, a trade group, at iihs.org/iihs/ratings.

How NHTSA's ratings work

NHTSA tests 90 to 150 vehicles each year. It conducts four tests: a head-on collision at 35 mph into a solid barrier; an angled crash at 20 mph into the front fender on the driver's side, as if hitting a pole; a side crash in which a 3,015-lb. barrier slams into the side of the vehicle at 38.5 mph, simulating a T-bone crash at an intersection; and a rollover stability test to see how easily a vehicle will tip over. It uses a star system to rank vehicles; five stars is best.

The head-on front crash results should be compared only to results from other vehicles of the same weight, NHTSA cautions. The other results allow you to compare any vehicle with any other, regardless of size, type and weight.


How IIHS's ratings work

IIHS tests about 80 vehicles per year. It conducts five tests, rating vehicles from good to poor on each test, and uses those results to determine if the vehicles qualify for its Top Safety Pick and Top Safety Pick+ ratings. It evaluates crash warning and automatic braking systems, too.

Though the government and the private trade group use different tests, their results can be used together to help careful shoppers find safe vehicles.

"We recommend that consumers look for vehicles that earn our Top Safety Pick and Top Safety Pick+ designations and that get four or five stars in NHTSA's tests," says Russ Rader, spokesman at the IIHS. "A vehicle should be able to do well in both sets of evaluations."

Both IIHS and NHTSA caution that you shouldn't make a snap judgment because of what appear to be good ratings. That's because overall ratings are made up of ratings in several tests. So look carefully at the data behind the overall score.

Even highly rated vehicles can have issues

For example, IIHS lately has been ranking headlight performance, and it's found that a model scoring high on crash tests might have only acceptable ratings for lights. Or some versions of that vehicle might have poor lights, while others have good lights.

A rating like that is especially important for older drivers because vision tends to decline with age and, according to the American Medical Association, it may be "much worse at night or during storms" — two times you rely on headlights.

Some examples of how headlights might not match a vehicle's overall rating:

  • The 2017 Ford F-150 pickup earns a Top Safety Pick from IIHS, but its headlights get the lowest score, poor.

  • Honda's new-design 2017 Ridgeline pickup gets IIHS's Top Safety Pick+, the highest rating, and has outstanding headlights — if you choose the highest-price models with LED low-beam lights. Without the LED low beams, IIHS says, Ridgeline's headlights are poor.

Not all vehicles have been independently tested

Some 40 brands sell upwards of 300 different models in the U.S. — too many for the government or the trade group to crash-test each one.

NHTSA says it buys from dealers the models it tests and concentrates on vehicles that are new to the market or have been redesigned.

IIHS ranks not only the vehicles it crash-tests at its lab in Ruckersville, Va., but also uses those scores to rate other, untested, vehicles "if they are built on the same platform," IIHS says. In addition, the trade group says a test of a vehicle from one model year may apply to earlier or later model years if the vehicle hasn't been significantly redesigned.

For instance, General Motors' Chevrolet Traverse, GMC Acadia and Buick Enclave crossover SUVs are on the same platform, which hasn't changed significantly in years. IIHS tested the 2008 Acadia and says the results apply to current models of the two others. GMC overhauled and downsized the Acadia for 2017, but its scores are good on all the tests, same as its predecessors.

And some ratings "apply only to vehicles with some optional equipment," says the IIHS's Rader.

So don't generalize. If you're car shopping, be sure to look at the ratings for the specific model you want to buy.


Here are some other things to keep in mind:

Similar scores don't guarantee similar safety. "A bigger, heavier vehicle provides better crash protection than a smaller, lighter one, assuming no other differences," IIHS says, even if big and small models have similar safety scores.

Not all occupants get the same crash protection. Some automakers reinforce the driver's side to pass IIHS' "small overlap" test, which simulates crashing into a pole or tree on the driver's side, but don't similarly upgrade the passenger's side safety structure.

And back-seat occupants don't have front-impact airbags to help absorb crash forces, as front occupants do.

Old and new scores can't always be compared with each other. That's because tests have changed.

Because NHTSA made its crash tests stricter for 2011 and subsequent years, the agency notes that a pre-2011 vehicle that received five stars under the old system "may receive a lower score under the new system, even if no changes have been made to the model."

So don't assume that the 2010 version of a sedan that got top ratings when new is as crashworthy as the 2017 version that has top ratings — or even the 2011 version.

Ratings aren't the whole picture. Even if you carefully sift the IIHS and NHTSA scores, you still want to consider additional safety gear, NHTSA advises. It recommends these: forward collision warning and automatic braking (both of which IIHS requires for its Top Safety Pick+ rating); lane departure warning to alert you if the car drifts into an adjoining road lane; and rear-view camera for safe backing and parking.

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