Car Safety Ratings: How to Read Between the Stars

Understanding your car's crash test rating

Aaron Miller | 

Mar 16, 2018 | 6 min read

Let’s say you’re in the market for a new, or at least new-to-you vehicle. In the course of your due diligence, you research everything from fuel economy to depreciation and the total cost of ownership. After emerging from a sea of numbers, you start looking into safety ratings. While your leading choice has a reassuring five-star crash test rating from the National Highway Transportation Safety Administration (NHTSA), for some reason it isn’t even considered a “Top Safety Pick” by the Insurance Institute for Highway Safety (IIHS).

What gives? Why are safety ratings so different from one test to the next, and how are you supposed to figure out which ones to trust?

Car safety ratings come from two key sources

In the United States, there are two major testing standards:

• The NHTSA is a government agency, and is responsible for those five-star crash ratings you see on window stickers.
• The IIHS is its non-governmental counterpart, and the independent, nonprofit organization holds cars to a different set of standards, and bestows either a “Top Safety Pick” or “Top Safety Pick+” rating (TSP and TSP+, respectively).

At a basic level, testing by both agencies have a lot in common: like the grown-up version of a rambunctious toddler trying to destroy his or her Hot Wheels, both conduct numerous crash tests.

The key difference is that NHTSA is not yet testing some of the newest safety systems available on cars, such as automatic emergency braking and lane keep assist, among others. IIHS, meanwhile, not only requires some sort of crash mitigation system, it tests its effectiveness.

Understanding the five-star car safety rating system

The simplest way to describe the NHTSA five-star rating system is that a three-star rating is average. That doesn’t mean a vehicle with a five-star rating is infallible, nor does it mean that you’ll be injured driving over a particularly harsh speed bump in a one-star-rated vehicle. Automotive safety has progressed so much over the last few decades, that even the lowest-rated new vehicles are safer than even the highest rated cars you grew up riding in.

This crash test video of a 1959 Chevrolet Impala colliding with a 2009 Impala illustrates the point.

NHTSA’s overall rating is a combination of how a vehicle performs in a series of crash tests. These include a frontal collision, a pair of side-impact tests that simulate both a “t-bone” collision and crashing into a phone poll, and a rollover resistance test. It’s important to note that while some of the tests can be compared among any vehicle, you can only compare a vehicle’s overall score against other vehicles from a similar category. No cars versus trucks, for example.

NHTSA does omit some crucial bits of information

Accurately crash testing a car is very complex, and as more sophisticated technology is added with each new model introduced, the NHTSA ratings haven’t kept pace. The agency notes the presence of safety systems designed to lessen the severity of an impending collision, such as automatic emergency braking, but doesn’t test those systems. Thus, what you’re getting in the test results is exactly that: the safety during a severe collision, but not the vehicle’s ability to soften the blow or avoid the crash entirely.

Also, pay attention to a � symbol if it appears in the ratings. There are some ways cars fail during testing that won’t make it into the score. If a door flies open during the impact, for example, or the fuel tank decides to do its best reenactment of Titanic Versus the Iceberg, the score isn’t impacted so long as the rest of the car holds up and the dummies are none the worse for wear. Instead, the failure is noted with a � symbol.

How a car becomes an ‘Top Safety Pick’

To qualify for either of the institute’s safety ratings (TSP or TSP+), the vehicle must not only protect passengers during collisions, but perform well during crash mitigation (for example, forward collision warning and automatic emergency braking) and headlight effectiveness testing.

In that regard, IIHS employs a higher degree of sophistication, and it even developed a few “overlap” crashes that NHTSA doesn’t perform.

If a vehicle comes equipped with a forward collision warning, it must successfully warn the driver within a specified range. If it passes, the car qualifies for the equivalent of a participation badge, but more importantly, is halfway to an advanced rating in crash avoidance. For vehicles with an automatic emergency braking system, the system is tested at 12 and 25 mph, and scored based on the amount of speed it is able to reduce before the impact. Assuming the car performs well enough, it can qualify for an advanced or superior rating.

Next, headlights are tested for how well they illuminate the road between 500 and 800 feet ahead, including through curves. Then, the amount of glare they cause for oncoming traffic, with both their high and low beams, is checked. When the first headlight rankings came out a few years ago, only a few vehicles qualified for an “acceptable” score, let alone a “good” rating. While the number of vehicles with a “good” headlight rating isn’t terribly high, it, along with an “advanced” crash mitigation system score, is a prerequisite to earn the coveted TSP+ overall rating.

Beware cars that pass but only with certain options

Here’s where things get tricky. On some vehicles, advanced driver aids like automatic emergency braking are available only as an extra-cost option. Similarly, some require upgrades if you want dynamic headlights that pass the IIHS standard. If you’re planning on shelling out for these features on a car that meets TSP or TSP+ criteria, that’s great.

Peruse the list of cars that qualify for TSP and TSP+ ratings, and you’ll see example after example that may earn the award, but only when equipped with various packages. In other words, if you’re interested in one of these vehicles, pay attention to the specific trim level that earned the TSP+ rating.

Using the safety rating systems to make a confident choice

By looking at test results from both NHTSA and IIHS, you can glean a fairly detailed overview of a vehicle’s strengths and weaknesses. Digging deeper, you can see exactly how a car may have failed – even when the score says it passed. Ultimately, these details, rather than the overall score, that will likely help you make a decision when considering the overall safety of two vehicles, or whether or not to spend extra for advanced safety technologies.

Aaron Miller

As a veteran automotive journalist, I have been fortunate enough to drive some of the most desirable cars on the planet and get to know some of the most important people in the industry. Before joining Capital One, I served as the Cars Editor for a major national website, and covered industry news and analysis for well-known automotive-specific sites. I also wrote feature articles and reviews for niche enthusiast websites. I’ve been obsessed with cars since—literally—before I can remember, with my collection of die-cast and slot cars taking center stage during my formative years. Simply put, for me, working isn’t really “work.”