Roof strength an important factor in vehicle rollover fatalities

Fatalities in rollovers are higher than in other types of crashes, accounting for 33 per cent of deaths in passenger vehicle crashes, even though only 3 per cent of crashes involved a rollover (US government statistics from 2002).

Early in November, 21-year-old Terry McCall was driving his truck Northbound on Route 28 in Cheswick, Pennsylvania, just outside of Pittsburgh. Without warning, McCall lost control of his vehicle, striking a guiderail and flipping for a distance of some 150 feet.

Authorities quickly responded to the scene as the pickup burst into flames. Amazingly, McCall and another occupant of the vehicle were pulled free and taken to the hospital without major injuries. 

Considering the extremely dangerous nature of vehicle rollovers, it is nothing short of a miracle that all parties in that Pennsylvania crash escaped with their lives. Structural improvements to modern vehicles, like increased roof strength, have helped make some automobiles safer in rollover crashes. Even so, the type of accident recently seen on Route 28 is still disproportionally responsible for severe injuries and deaths.

Rollovers Responsible For Thousands of Deaths Annually

A vehicle is classified as rolling over if, at any time in the course of an accident, it tips onto its side or onto its roof. In many rollovers, vehicle occupants are fully or partially ejected, which substantially increases the likelihood of suffering serious injury or death.

Vehicle rollovers have a much higher fatality rate than other kinds of automobile crashes. Less than three percent of all crashes involve vehicle rollovers. Yet, rollovers account for more than 33 percent of all passenger vehicle occupant deaths. In 2009, out of 23,437 total passenger vehicle occupant deaths, 8,296 were among vehicle occupants whose automobile had rolled.

Roof Strength Ratings Help Consumers Judge Rollover Safety

There are several automobile features that can help prevent vehicle rollovers or lessen the chances of injury in a rollover accident -- effective seatbelts, electronic stability control and side curtain airbags, to name a few. But one rollover safety feature has received particular attention in recent years: vehicle roof strength.

For a long time, a debate raged among experts as to whether roof strength and serious head and neck injuries were causally related in vehicle rollovers. Some researchers maintained that occupants in rollovers are injured when they "dive" into the vehicle roof before if crushes, while others asserted that the roof buckling into the passenger compartment often contacts the people inside, causing injury.

A series of intensive studies by the Insurance Institute for Highway Safety seem to have finally put the controversy to rest. The IIHS research showed that stronger roofs both reduced the risk of ejection, and cut the chances of suffering serious injury for occupants remaining in the vehicle during rollovers. One IIHS study of 12 small car models found that compared to those riding in weaker counterparts, occupants of cars with the strongest roofs faced a 39 percent lower ejection risk in a vehicle rollover, as well as a 35 percent reduction in serious injuries or deaths. Two subsequent National Highway Traffic Safety Administration studies confirmed these results.

Today, the IIHS rates new vehicles for rollover strength with their familiar Good/Acceptable/Marginal/Poor rating scale. Ratings are determined by comparing a particular vehicle model's weight to its roof strength, measured by a crush test that simulates the kind of pressure a vehicle roof would face in a real rollover accident.

Model year 2010 vehicles were the first to be tested under the new roof strength standards. Overall, there was very little predictability about how particular models or vehicle classes would perform -- vehicle size turned out to be a nonissue, as the only relevant factor in the crush testing is a vehicle's weight relative to its roof strength. However, hybrid automobiles tended to earn lower ratings than gas-only models, as the added mass of hybrid batteries and hardware components unfavorably shifted the weight to strength ratio, at least for vehicles without reinforced roofs.

One of the criteria for achieving an IIHS Top Safety Pick designation is the receipt of "Good" ratings in all the organization's safety tests, including frontal-offset, side-impact and rear-crash protection. Requiring a "Good" roof strength rating for Top Safety Pick models since 2010 has knocked many vehicles out of the elite group.

Among the many safety features available on today's automobiles, it is easy to overlook something as simple as roof strength. Nonetheless, paying attention to the new roof strength ratings is important, and well worth the time to ensure the safety of your loved ones.