The National Highway Traffic Safety Administration (NHTSA) rates a vehicle’s rollover potential in two different ways: First, it determines a vehicle’s static stability factor (SSF), or a calculation of rollover resistance while the vehicle is at rest. The second measure is an on-road rollover test that examines how likely a vehicle is to tip based on its handling. A vehicle’s rollover resistance (given from one to five stars) is then based on a combination of both on-road and at-rest test scores.
The on-road test is performed on most new SUVs, pickup trucks, and minivans. These vehicles go through a series of typical road maneuvers, including a quick left-right turn, a fishhook turn, and speeds that increase from 35 to 50 mph (to discover how the vehicle responds to a sudden change in direction). If the vehicle lifts two wheels off the ground during any maneuver, it has failed the test; if the vehicle keeps all wheels on the ground (or slides, but recovers), it passes.
How SUV “Star” Ratings May Differ from True Rollover Protection
Even if your vehicle was given a multiple-star safety rating, you should know that this does not necessarily mean you are at less risk of a rollover crash—especially if you drive an SUV. Although many SUVs have “tipped up” during NHTSA on-road testing, their star ratings are minimally affected by the failure. This is because the government's rollover ratings rely much more on SSF than on-road testing, despite the fact that the road test is a more true-to-life demonstration of the vehicle’s responses in a crash.
If you drive an SUV or van, you should find out what your car’s rollover safety rating really is at www.safercar.gov. Here, you can find out each of your vehicle’s individual safety ratings as well as how your car scored on the on-road performance test (under Dynamic Test Result).
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