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Crash Test Ratings: What's Included in an NHTSA Rating?


author photo by Doug DeMuro April 2014

If you're interested in checking out crash test ratings to find out whether your next car is safe, you might want to know more than a simple number of stars. What does each rating mean? How does the National Highway Traffic Safety Administration (NHTSA) test cars? We have the answers.

Overall Rating

Since the 2011 model year, NHTSA has published four different crash test ratings for each vehicle. One is the overall rating, and it gives an overall picture of a car's crashworthiness. That's the rating used most often by NHTSA and by automakers in marketing materials.

To get the overall rating, NHTSA averages a vehicle's scores from three other tests. There's a front-impact test, a side-impact test and a rollover assessment, each of which measure a different aspect of vehicle safety. We're explaining those tests below.

Front-Impact Test

The front-impact test involves two crash-test dummies placed in the two front seats of a car. The dummies are belted in, and the car is crashed into a fixed barrier at 35 miles per hour. NHTSA then measures potential injuries to both the driver and passenger dummies, based on instruments located all over the dummies' bodies, including on their head, neck and torso.

Interestingly, not all front-impact test scores are alike. Since the scores are determined by comparing crashworthiness to other cars in the same segment, a large vehicle that achieves four stars may actually have a lower likelihood of injury than a small vehicle that achieves five stars. In other words, comparing two front-impact scores requires making an apples-to-apples comparison of cars in a similar weight and size class. It's also important to note that the front-impact test doesn't examine a car's crashworthiness for rear passengers.

Side-Impact Test

NHTSA's side-impact test actually involves two tests whose scores are averaged together in order to return one single side-impact score. In the first test, adult-sized dummies are placed in the driver's seat and the rear seat on the driver's side. The car is then hit directly from the side with a 3,015-lb barrier at 38 mph. Dummies are then examined for injuries to the head, chest, abdomen and pelvis.

The second test is performed using only one dummy, located in the driver's seat. In that test, the car is pulled into a large pole at 25 mph, simulating an impact with a tree or utility pole. After the accident, the dummy is examined for potential injury to its head, chest, lower spine, abdomen and pelvis.

Rollover Test

The final component of NHTSA's testing program is the so-called rollover test. This isn't really a test at all, however. Instead, the rollover assessment is a mathematical formula that takes into account a car's width and center of gravity to determine its likelihood of rolling over. In other words, NHTSA doesn't actually test cars for rollover risk, though the agency says that the test is valid, given comparisons with rollover statistics from actual car crashes.

In all, NHTSA crash test ratings give us a good indication of a vehicle's ability to hold up in a serious crash, and the agency is continually refining its measures to continue helping car shoppers find the safest possible vehicles.

This image is a stock photo and is not an exact representation of any vehicle offered for sale. Advertised vehicles of this model may have styling, trim levels, colors and optional equipment that differ from the stock photo.
Crash Test Ratings: What's Included in an NHTSA Rating? - Autotrader