Rollover Crashworthiness and Countermeasures

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.

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.

For the past 40 years, CfIR's focus has been on rollover crashworthiness and occupant safety. Using accepted scientific methodology, our crashworthiness research has included:

  1. 1. Quasistatic Roof Strength Fixture Design and Testing (FMVSS 216, M216)

  2. 2. Dynamic Rollover Fixture Design and Testing of Dummy-Occupied Vehicles (JRS 2003, JRS II 2011, Nash Carousel)

  3. 3. Rollover Countermeasures (HALO device)

  4. 4. Briefings and NHTSA Docket Submissions