Prior to 2000, before Electronic Stability Control (ESC) one-third of all LTV fatalities occurred in rollovers. LTV's are much more likely to roll over than passenger cars because of their higher CG. SUV's have the highest rollover rate and rollover fatality rate. Large trucks are probably most vulnerable to rollover because of their relatively high CG, particularly when loaded. Experienced professional drivers are well aware of their potential instability.



Most rollovers occur when a driver loses control of a vehicle, and it begins to slide sideways. When this happens, something can cause the vehicle to “trip” and cause it to roll over. A few explanations could be a curb, guardrail, tree stump, or soft or no shoulder on the side of the road. When the driver tries to turn a vehicle too forcefully and at a high rate of speed or with a tight turning radius, frictional force between the tires and road surface can cause the vehicle to tip up and then roll over. Many rollovers are single-vehicle crashes. A collision may precipitate a rollover by initiating the rolling motion too fast or causing the vehicles to be redirected sideways, such as in a t-bone.

Roof crush in rollovers is caused by weak roof pillars and windshield header that are not strong enough to hold up the weight of the vehicle as it hits the ground, so it intrudes into the occupant space. In rollovers, roof crush causes side window failures creating ejection portals for occupants to be thrown from the vehicle. The largest number of casualties in rollovers is from ejection. Roof crush also causes a significant number of head and neck injuries, typically the most severe consequences of rollovers.

NHTSA Defines the Scope and Purpose of the FMVSS 216 Roof Crush Resistance Compliance Test:



Scope: This standard establishes strength requirements for the passenger compartment roof.

This standard establishes strength requirements for the passenger compartment roof.

Purpose: The purpose of this standard is to reduce deaths and injuries due to the crushing of the roof into the occupant compartment in rollover crashes.

The U.S., European and Australian NCAP and the IIHS produce ratings of new vehicle performance based on dynamic crash tests in frontal, side and rear crashes, and vehicle handling tests. No dynamic-based crashworthiness ratings exist to date for new vehicle performance based on rollover crashes. There is no rating for rollover occupant protection, a crash mode responsible for one-third of all light vehicle occupant fatalities. NHTSA has upgraded the roof crush requirements for new cars, but the time is overdue for an NCAP rating on rollover survivability.

FMVSS 216/216A: Safercar.gov publishes “star ratings” of U.S. vehicles in all accident modes. The rollover ratings are based on an SSF.

The SSF of a vehicle is an at-rest calculation of its rollover resistance based on its most important geometric properties. The SSF is a measure of how top-heavy vehicle is. The SSF only tells you how likely it is for the vehicle to rollover, NOT how well the vehicle structure will hold up if it does roll!

A vehicle's SSF is calculated using the formula SSF = T/2H, where T is the “Track Width“ and H is the “Height of the CG.” The track width is the distance between the centers of the right and left tires along the axle. The location of the CG is measured in a laboratory represents the height above the ground of the vehicle's mass. The lower the SSF number, the more likely the vehicle is to roll over in a single-vehicle crash.