What Are IIHS Ratings?

What Are IIHS Ratings?

Sometimes safety takes a back seat to horsepower, vehicle design and luxury amenities but when you’re in a crash it’s really the only thing that matters.

So what if you’re sports car can hit 60 miles an hour in less than four seconds? Who cares if your flagships sedan has a Champagne cooler in the back seat? When you sideswipe an oak tree or get rear-ended by a drunk driver your life hangs in the balance.

It’s Pronounced Nit-Suh

NHTSA LogoThe National Highway Traffic Safety Administration, NHTSA for short, rates vehicle crashworthiness. To make things easy for people to understand they use a five-star scale where one is lowest and five is best. You’ll often see these scores printed on window stickers. This federal agency evaluates how cars and trucks perform in frontal crashes, side impacts and rollover accidents, though they’re not able to rate every single car and truck sold.

To encourage continuous safety advancements NHTSA has added additional tests and variables to its repertoire over the years. For instance they’ve implemented a side-impact pole test, they also use different-sized dummies and collect more data points from crashes.

We reached out to them asking about their testing methods and how they compare to the ones employed by the Insurance Institute for Highway Safety (IIHS), an unaffiliated group that also performs safety evaluations. Additionally we asked which methodology they thought was better. In a statement we received via e-mail NHTSA said:

“The National Highway Traffic Safety Administration (NHTSA) is committed to improving safety on the nation’s roadways and helping motorists make informed decisions about new or used vehicles they are considering. The agency’s five-Star Safety Ratings program is designed to provide consumers with information about the crash protection and rollover safety of new vehicles beyond what is required by federal standards.”

NHTSA’s tests are designed to help drivers compare the crashworthiness of different vehicles on the market. They also encourage manufacturers to design and engineer safer cars and trucks. They’ve been smashing up vehicles in the name of science since the late 1970s but they’re not the only game in town.

Reaching Higher

IIHS LogoThe IIHS is a not-for-profit group that’s dedicated to helping prevent human and monetary losses associated with accidents. That’s a high-minded goal but they’re better known for their demanding crash tests and the smashed-up cars that result from them.

Russ Rader, senior vice president of communications at IIHS said, “We’re funded entirely by automobile insurance companies with the mission of finding ways to reduce the deaths, injuries and property damage that results from motor-vehicle crashes.”

SEE ALSO: Why Rear-Drive Cars Struggle in Small-Overlap Test

“Safety is a priority when choosing a new vehicle,” said Rader, adding, “Crash-test ratings from government and from IIHS are important because they show differences among vehicles [and] go beyond the safety standards that manufacturers have to adhere to.”

Fiat 500L Small-Overlap CrashRader said, “People assume that if a vehicle is for sale in the market that it is safe,” but this isn’t true. In order to be sold in the United States all a car or truck has to do is meet FMVSS, which stands of Federal Motor Vehicle Safety Standards. These rules govern things like bumper design and how windshields are affixed to the body, not necessarily crash performance.

Comparing the two separate test procedures Rader said, “Generally NHTSA’s tests are a good measure of how well seatbelts and airbags are working to protect people in crashes. The institute’s tests tend to be more demanding of a vehicle’s structure.” He also noted that both sets of tests are a step up from basic safety standards.

IIHS assess motorcars in several ways. They test head restraints and seats, roof strength, side-impact performance and even factor in accident-prevention technology, but they’re probably most famous for two separate crash evaluations, the moderate-overlap and small-overlap tests.

They’ve been conducting moderate-overlap crash evaluations since 1995. In this test a vehicle is plowed at 40 MPH into a barrier covered with a deformable, energy-absorbing section that’s made from an aluminum honeycomb. Forty percent of the vehicle’s front impacts this barrier.

In the much more demanding small-overlap test cars and trucks are rammed into a similar immovable obstacle at the same velocity except there’s no padding and only 25 percent of the vehicle’s front end hits the barrier.

SEE ALSO: Small SUVs Fare Poorly in IIHS Small-Overlap Crash Test

“The small overlap test is more challenging … because the main energy absorbing structures in the front of the vehicle are typically centered in the middle of the front end,” Rader said. Many automotive architectures can’t handle the forces generated by a glancing blow like this and consequently they don’t fare well in the small-overlap crash test.

Crash-Test Graphic

Still, “Some manufacturers were paying more attention than others,” Rader said. Going further he mentioned that IIHS made automakers aware of the small-overlap test long before it was introduced in 2012. “We didn’t spring it on them,” he said.

IIHS Small-Overlap CrashIn all IIHS crash tests a vehicle can receive one of four different scores; good is the best, followed by acceptable, marginal and then poor. If a particular model does well in all areas it might be given a Top Safety Pick award. If it achieves all of that and is equipped with some sort of crash-avoidance system like automatic braking or at the very least forward collision warning it may also earn Top Safety Pick+ honors, the highest accolade awarded.

Method to the Madness

But where did the IIHS come up with its small-overlap evaluation? Rader said, “Crash tests aren’t just developed willy-nilly, they’re based on research on what’s happening in crashes to people in the real world.”

“We looked at crashes in which people were doing the right thing,” said Rader, which includes driving a vehicle that performed well in both NHTSA and IIHS tests. “The study showed that about a quarter of the serious injuries and deaths in frontal-impact crashes occurred in small-overlap type impacts.” Given the significance of these kinds of crashes IIHS decided to implement their demanding small-overlap test.

Sobering Statistics

What does all of that mean? Can such a nebulous thing be quantified? As a matter of fact, yes. Rader said in 2012 there were 33,561 motor vehicle crash deaths in the United States, a total that includes car accidents, people that died in trucks, pedestrians hit by vehicles and other things like that. He said, “The number of people killed in frontal impacts was 11,426.”


Additionally Rader said, “Rollovers accounted for about 7,500 deaths in 2012 … It’s a significant problem.”

Still Rader said, “Vehicle safety improvements are the main reason that the highway death toll is at a record low.” Things like better crash worthiness, crumple zones and anti-lock brakes have really made a difference. But even better than these items he said, “There’s a triumvirate of important safety features, seat belts, air bags and electronic stability control.” Additionally, “Almost 85 percent of drivers observed on the road are wearing their belt,” which is always a smart idea.

Sound Suggestions

Of course there’s more to crashworthiness than just test scores; the laws of physics never take a day off. Accordingly Rader said, “If you’re looking for a safe vehicle you should avoid the smallest cars on the road.”

IIHS Ratings

Sure, tiny vehicles are typically super efficient and safer than they’ve ever been but for drivers that are worried about accidents Russ said, “A midsize car or larger with good crash-test ratings is a safe bet.”

Take a Look, It’s in a Boo … It’s on the Web

Both IIHS and NHTSA safety evaluations go above and beyond what’s required by law. Savvy shoppers are wise to research a vehicle’s crash performance in both tests before they sign their life away. The small-overlap test performed by the IIHS is particularly demanding. If a vehicle can earn a top score in this category then it’s probably a good bet that it will keep you safe should the unthinkable happen.

Check out even more safety-related stories!