Unlike front and side crashes, which can vary greatly in severity from minor to major, rollovers, by definition, tend to be severe crashes because of the energy required to roll a vehicle over. Due to their severity, rollovers account for about one-third of all crash fatalities, even though they account for less than 10 percent of all crashes. More importantly, nearly 80 percent of rollover fatalities involve people not wearing safety belts. Safety belts are extremely effective in reducing the risk of serious and fatal injuries in these crashes. Real-world data indicate that more than 90 percent of safety-belted occupants in rollovers escape without a serious injury, and NHTSA estimates that safety belts are 74–80 percent effective in preventing fatalities in rollovers.
Recently, attention has focused on whether there is a relationship between roof strength and occupant safety in rollovers. Due to the severe nature of rollover crashes, there is often roof deformation or crush in those crashes involving a serious injury or fatality. When there is roof deformation present and a serious injury or fatality, the common misconception is to assume that the deformation caused the injury or fatality.
Ford Motor Company has conducted extensive research and testing to examine the purported relationship between roof strength/deformation and injury in rollovers. Real-world accident data and laboratory testing have demonstrated that increasing roof strength levels beyond the current NHTSA requirements, by itself, does not significantly enhance safety in rollovers. Rollover crash testing comparing vehicles with production roofs to vehicles with reinforced, roll-caged roofs has demonstrated that the injurious forces acting on safety-belted crash-test dummies occur before there is any significant roof deformation in the vehicles with production roofs. Furthermore, these forces also occur in roll-caged vehicles. There is no meaningful difference between them.
How do we explain these results? The rotational forces acting on belted occupants in rollovers can result in the occupant's head being close to, or in contact with, the roof before the roof contacts the ground. When the roof strikes the ground, the occupant's head simultaneously strikes the ground (with the roof sheet metal in between), resulting in a potentially injurious impact. The injury from this impact occurs prior to significant deformation of the roof. Other vehicle manufacturers and numerous researchers have conducted similar testing, and their findings are consistent with Ford's.
Ford is a leader in researching and developing technologies, including our Roll Stability Control™ system (see Vehicle Safety), to help reduce the risk of rollovers, as well as systems to help further enhance occupant protection should a rollover occur. We are conducting research into advanced safety belt systems that may have the potential to further reduce occupant motion in rollovers. We also continue to evolve the design of our rollover-deploying side air curtains, known as the Safety Canopy™, to help further reduce the chance of being ejected in a rollover. As safety belt and ejection reduction technologies progress, there may be the potential in the future to further reduce the risk of injury in rollovers by combining these technologies with revised roof and vehicle structures.
