What the stars don’t say

Crash tests are useful for gauging how well a vehicle can protect occupants in a crash, but no test is infallible or universal. For instance, most tests use a 50th-percentile (average sized) crash-test dummy, and people much smaller or larger than that may not be protected as well as the scores indicate. Here are some other factors that affect how you should view the scores:

Heavy vs. light vehicles

Since the front-crash tests performed by NHTSA and IIHS simulate a collision between two vehicles of the same weight and height, the scores don't apply to crashes between mismatched vehicles. In a crash between a big car and a small one, you're usually better off in the big car. In such cases, the larger, heavier vehicle projects more of its crash energy into the smaller one. This, in turn, helps to better protect the larger vehicle's occupants, but it can inflict proportionately more injury to the occupants of the smaller vehicle.

Higher bumpers

Besides their weight, the higher bumper on many taller vehicles such as pickups and SUVs contributes to the truck vs. car mismatch. When an SUV or truck hits a typical passenger car, the impact occurs above the car's bumper line, exerting its force into weaker portions of the smaller vehicle and inflicting greater damage. To address this, many SUVs—especially car-based models—are being designed with lower, more compatible bumpers.

More on the side

Side-impact tests apply more broadly than front-crash results do. Since the striking vehicle is the same within all the NHTSA tests and within all the IIHS tests, the results apply across all classes. In other words, a Good side crash score for a small car is the same as a Good for a large car.