IIHS Safety Ratings: What Do They Mean?
Many automakers like to tout the Top Safety Pick+ or Top Safety Pick ratings that their models receive from the Insurance Institute for Highway Safety. The IIHS tests vehicles annually and rates how well they withstand, mitigate, and avoid crashes. What types of tests does the IIHS perform to arrive at its ratings, and what do they mean? Here’s what you need to know.
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What the IIHS does
Insurance companies originally started the IIHS in 1959 with a mission to promote safety on the road. Today, the IIHS operates as an independent nonprofit and performs its own research on how to prevent vehicle crashes. The organization’s experts also study a wide range of other issues related to drivers, vehicles, and roadways.
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Determining IIHS ratings
According to the IIHS, a vehicle’s performance on most tests (including crashworthiness, headlights, and LATCH usability) is graded poor, marginal, acceptable, or good. Front crash prevention receives basic, advanced, or superior ratings.
To attain an IIHS Top Safety Pick rating, a 2020 model year vehicle must achieve good ratings in all crash tests. It must receive an advanced or superior rating for its available systems that prevent or mitigate collisions with pedestrians and other vehicles. It must also be available with acceptable or good headlights.
A Top Safety Pick+ model must meet the same criteria, along with one more stringent requirement: Acceptable or good headlights must come standard.
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Crashworthiness tests
Six crash tests lie at the heart of what the IIHS does. These include three frontal crash tests, a side crash test, a roof strength test, and a test for seats and head restraints.
Moderate overlap frontal test: In this test, a crash dummy is placed in the driver’s seat. The vehicle is then rammed into a barrier that covers about 40 percent of the vehicle’s width. The goal is to recreate a frontal crash between two vehicles both traveling at about 40 mph.
Driver-side and passenger side small overlap frontal tests: In these tests, the vehicle is driven into a barrier that covers 25 percent of its width on either the left or the right — just as if it was striking a narrower object like a utility pole or a tree. Vehicles are designed with crumple zones to absorb crash energy and keep occupants from being injured by parts intruding into the passenger compartment. However, vehicles’ edges aren’t always included in these zones, and a small overlap crash can cause wheels or other components to enter the cabin and cause injuries. Small overlap tests help ensure that vehicles properly protect all passengers in a wider range of crash situations.
To get a good rating in these three crash tests, a vehicle’s crumple zones and safety cage must hold up well during frontal crashes. The model must also limit injury risk and occupant movement during those types of crashes. Crash tests are performed at different levels of intensity depending on the weight and type of vehicle.
Side crash test: In this test, a 3,300-pound barrier traveling 31 mph is smashed into the driver’s side to see how well a small woman in the front seat and a child in the rear seat would be protected. The test’s criteria include safety cage performance injury prevention, and head protection. Over time, this test has encouraged automakers to develop side air-bag systems and bolster other side protections.
Roof strength test: This tests how well a vehicle maintains structural integrity and protects its occupants in a rollover crash. A metal plate is forced at an angle into the roof to see how much force will crush the roof. For a vehicle to be rated good, its roof must hold up against force that’s at least four times the vehicle’s weight.
Head restraints and seats test: This test uses a dummy and a sled to measure how well a vehicle’s seats and head restraints prevent whiplash and other neck injuries during a rear impact. The twin criteria for this test are geometric (whether a head restraint is positioned appropriately) and dynamic (how supportive the seat is during the impact). If a vehicle offers a variety of seat options, testing is typically done on the one that’s most widely available.
Crash avoidance and mitigation tests
As driver-assist technology has advanced, the IIHS has incorporated a handful of crash avoidance and mitigation tests into its ratings.
Front crash prevention tests: These tests assess a vehicle’s available forward collision warning and automatic emergency braking technologies. For collisions with other vehicles, models are tested at speeds of 12 mph and 25 mph to see how well their systems reduce speed and avert collisions. Vehicles are also tested in a variety of scenarios and speeds to find out how well they prevent crashes with pedestrians. If a vehicle has collision warning but not automatic braking capability, it can’t earn more than a rating of basic.
Headlight test: The IIHS tests how extensively a vehicle’s headlights illuminate the roadway on straightaways, gradual curves, and sharp curves. It also measures how well they prevent glare for oncoming drivers. These tests are conducted using both low beams and high beams. Headlight systems with advanced features like curve-adaptive operation and automatic high beams often perform better. Even with the rise of these technologies, IIHS notes that many modern vehicles have lackluster, poorly aimed headlights.
LATCH tests: Most vehicles must have at least two LATCH (Lower Anchors and Tethers for Children) systems to hold rear child seats securely in place. IIHS rates LATCH systems according to how accessible the lower anchors are, how much force is required to attach a seat, how easy the system’s angle is to work with, where the system is located, and how confusing it is. A vehicle must meet all five of these criteria to attain a good rating.
What about NHTSA ratings?
The National Highway Traffic Safety Administration performs its own tests and issues its own ratings to measure vehicles’ crashworthiness. These differ in a variety of ways from the IIHS, although both groups aim to help car buyers find the safest vehicles possible. A high rating from the NHTSA doesn’t mean exactly the same thing as a high rating from the IIHS. However, if a vehicle boasts strong ratings from both the NHTSA and the IIHS, that’s a very good sign.
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What to watch out for
It’s important to note that IIHS tests and criteria have changed over the years. So, if you’re buying a used Top Safety Pick+ model from 2017, the way IIHS arrived at that rating may be different than a vehicle from the current model year.
Keep in mind, too, that IIHS ratings often depend on available features. For example, Top Safety Pick ratings only apply to model variants that come with optional front crash prevention tech and optional acceptable or good headlights. If you opt for a model without those features, it won’t actually possess that rating.
However, if you’re considering model without a Top Safety Pick or Top Safety Pick+ rating, you can still check its crash test ratings. Even if a model doesn’t come with all the latest technologies, good IIHS crash test ratings indicate that it’s still likely to do a solid job protecting you and your loved ones in dangerous situations.
A longtime editor/writer and recently transplanted Hoosier, Caleb Cook lives in Xenia, Ohio. His favorite activities are reading and listening to music, although he occasionally emerges from the heap of books and vinyl records in his basement to stand blinking in the sunlight. Once fully acclimated to the outside world again, he can be observed hanging out with his wife, attempting a new recipe in the kitchen, attending movies, walking the dog, or wandering into a local brewery to inquire about what’s on tap. See more articles by Caleb.