We’ve all seen those videos. The ones where crash test dummies with yellow and black circles on their foreheads, elbows, knees, and chest are hurtled at varying speeds into walls, barriers, and other vehicles. While seeing the glass shatter and the airbags explode makes for some really fascinating viewing, the government does these tests for far more than just entertainment value. These are the tests that determine those safety ratings you see on both new and used cars, and they are the tests used to keep us safer on the road.
There are a few things you need to know about car safety, however. First there are two agencies that conduct the tests—the Insurance Institute of Highway Safety or IIHS, and the National Highway Transportation Safety Administration or NHTSA. The IIHS is funded by auto insurers and insurance associations, while NHTSA is funded by your federal taxes and part of the Department of Transportation.
It is important to consider results from both agencies as they give you two different kinds of information. NHTSA gives vehicles an overall rating out of five stars. Their testing includes front and side crash tests as well as and rollover tests. The IIHS puts cars through five different tests including side, small front overlap, moderate front overlap, head restraints, and seats. They then rate each car as good, acceptable, marginal or poor based on those tests. In addition to the crash tests, IIHS also does tests on crash avoidance and mitigation systems (like automatic braking etc.) that are included on a lot of new cars on the road today. In those tests they give cars a rating of basic, advanced, or superior, based on the type of system and its performance.
It’s also important to know that each agency does their tests differently. NHTSA uses a sled and wall that hit the vehicle straight on or directly from the side. The truth is, however that this isn’t how accidents occur in the real world. IIHS on the other hand uses a side impact and frontal tests that more closely mimic real world crashes, showing how well a vehicle takes a partial hit.
One thing to know about both IIHS and NHTSA—they don’t test every single model of every vehicle and they don’t test what they call low-volume cars. That means that luxury brands like Rolls-Royce, Aston Martin, and McLaren, don’t get crash ratings, though all of those companies do their own crash testing to ensure that passengers and occupants are safe should a crash occur. You won’t find any crash ratings for Porsches on NHTSA’s website, either. That’s because NHTSA buys all their cars at various dealerships across the country, and Porsches are very expensive. When shopping for a new or new-to-you car you should know that your exact model might not show up on either of the sites because both agencies target the models that they think will have high sales volume—and ones that the agency can afford. And despite common misperception that the cars that both agencies test are given to the agencies by car manufacturers—they are not.
You should also be aware that NHTSA and the IIHS do not go back and re-crash older models. The ratings you see for the cars in that model year, are the ratings they gave the vehicle in the context of the other vehicles in that model year. Basically a Top Safety Pick or 5-star rating from 2012, is simply not the same as it is in 2016.
The other thing to realize is, as Cars.com points out, you can’t really compare cars from model-to-model or year-to-year. Things about the cars change from one year to the next, as do things about the tests. For example, the IIHS just introduced the front small and moderate overlap tests back in 2012, so models before then won’t have those ratings. The other thing to know about the testing done by both agencies is that many of the tests are meant to replicate what would happen if the vehicle was in a collision with the same class of vehicle. This is the case with the frontal crash ratings. Neither agency tests how a vehicle would fare if it got into a crash with a heavier or lighter vehicle—they only test them against vehicles that are in the same weight class. That’s an important distinction to make too—since there are an increasing number of big, heavy SUVs on the road. So a big vehicle with a Poor rating isn’t necessarily less safe than a small vehicle with a Good rating since they are being crashed into vehicles of the same size and weight class. If you want to know more about Frontal Crash Test ratings check out our post on the topic, here.
Along those same lines, it’s important to know that the agencies change their designation rules from year-to-year, too. For example, one year the IIHS tested how well stationary seats protected against whiplash in a 20 mph rear crash. In order for a car to get a Top Safety Pick designation, a car had to get a good rating on that test. The next year however, vehicles had to get a score of “Good” on the roof strength test in order to earn a Top Safety Pick designation.
Finally, know that manufacturers can claim “safest car” or “IIHS Top Pick” only if they get that designation from the agencies. The Truth in Advertising laws force manufacturers to be honest in their claims and back up their claims with scientific fact. You can always visit the IIHS or NHTSA sites to see where your new or used car stacks up, but be sure to read the entire report. Just looking at the numerical ratings or labels doesn’t give you the complete picture.
So the next time you are shopping for a great used car, know that the safety tests and ratings you see from NHTSA and IIHS have their limitations. It’s important to keep this in mind as you compare different cars over different years. By knowing the constraints of safety testing, and being an informed consumer, you can make a better decision on your next car.
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