Roof strength
Discontinued test
We evaluated roof strength because it is crucial for maintaining occupant survival space during a rollover. Stronger roofs crush less, reducing the risk that people will be injured by contact with the roof itself. Stronger roofs also can prevent occupants, especially those who aren't using safety belts, from being ejected through windows, windshields or doors that have broken or opened because the roof has deformed.
How the test was run
The strength of the roof was determined by pushing an angled metal plate down on one side of the roof at a slow but constant speed and measuring the force required to crush the roof.
How vehicles were evaluated
- The force applied relative to the vehicle’s weight is known as the strength-to-weight ratio. We used the peak strength-to-weight ratio recorded at any time before the roof is crushed 5 inches as our key measurement of roof strength.
- A good rating required a strength-to-weight ratio of at least 4. In other words, the roof had to withstand a force of at least 4 times the vehicle’s weight before the plate crushed the roof 5 inches.
- For an acceptable rating, the minimum required strength-to-weight ratio was 3.25. For a marginal rating, it was 2.5, and anything lower than that was poor.
Why we stopped conducting this test
We discontinued the roof strength test because virtually all vehicles were earning good ratings, and an updated federal standard phased in between 2013 and 2017 was similar to our requirements for a good rating.
For details on other current and discontinued tests, visit the About our tests page.