Detroit automakers insist the existing rule is adequate
At a demonstration in Gothenburg, Sweden, Volvo rolled an XC-90 SUV in 2002. With a roof made from high-strength Boron steel, the XC-90 rolled more than three times. There was minor cosmetic damage to the roof, but no significant intrusion into the occupants’ safety cage.
Volvo also enhances safety by providing curtain-style airbags in all three rows of seats, reducing the likelihood of head injury. The SUV has a sensor that activates fractions of a second after a rollover begins, tightens seatbelts and keeps passengers in place.
WASHINGTON – To demonstrate how well its XC-90 sport utility vehicle would hold up in a rollover crash, the Swedish automaker Volvo invited reporters to a demonstration in the spring of 2002.
Volvo, owned by Ford Motor Co., conducted a test using specifications the U.S. government developed in the late 1960s.
At the company’s safety center in Gothenburg, Sweden, the SUV was loaded on a cart, which was accelerated to a speed of 30 mph. When the cart was brought to a sudden halt, the XC-90 went rolling, spinning more than three times before coming to a stop. At the end of the violent demonstration, the XC-90’s roof sustained only slight creasing and its windows were cracked.
The XC-90 has one of the strongest roof structures of any vehicle on the road today, according to safety experts.
While the need for a strong roof is emphasized by Volvo and other European automakers, their U.S. counterparts have insist there is no correlation between roof intrusion and serious injuries.
The Volvo roof is reinforced with boron steel, a high-strength alloy so hard that special factory tools are required to work with it. The alloy is 25 percent to 50 percent more expensive than conventional steel.
"We were entering a new segment, so it was natural for us to take the next step in the safety cage area, and introduce new technology," said Hans Wikman, project manager for the XC-90.
As a result, the XC-90 roof exceeds federal requirements by more than 100 percent, Volvo said.
During the test rollover, the SUV’s rollover sensors activated belt tighteners, keeping the crash-test dummies in place. Side-curtain air bags stretched along all three rows of seats, preventing violent head contact with the windows.
Why did Volvo add so much rollover safety technology?
"We had a heavier vehicle, with a higher center of gravity making it more prone to roll over," said Thomas Broberg, Volvo’s deputy director for research and development. "That’s just basic physics."
Ford takes different path
European automakers like Mercedes-Benz and GM-owned Saab follow similar regimens of testing to produce rollover-worthy cars and SUVs. Volkswagen, Toyota and BMW also conduct dolly rollover tests, according to company brochures.
But Volvo’s parent, Ford, General Motors Corp. and DaimlerChrysler AG’s Chrysler unit, follow a different path in developing its vehicles. Detroit’s automakers do not routinely conduct either dolly tests or tests where vehicles are suspended from cables and dropped on their roofs, according to court records and safety experts.
Ford conducts the basic government roof-crush test developed 33 years ago, and its internal company safety standard exceeds government requirements 25 percent, the company has said in court.
The test, known as Federal Motor Vehicle Safety Standard 216, is conducted by gradually applying pressure to a steel plate on one side of the roof. Critics contend its doesn’t emmulate real-world rollover conditions.
Steve Forrest, an engineer who has analyzed Ford documents in rollover trials, said it is clear that the company routinely takes weight out of the roof structure to save money and maximize fuel efficiency. He calls it "designing down to the standard."
Part of this is the natural process of engineering, the need to balance other regulatory requirements – such as fuel economy mandates – and consumer features against what is required to pass the roof-strength test.
Critics say the result is weaker roofs.
Jim Ragan, an attorney who has retained exhibits from a roof-crush case in a warehouse in Corpus Christi, Texas, says the standard Ford F-150 roof from 1980 through 1996 looks less substantial than earlier models.
Ford declined interviewed requests for this series, referring questions to the Alliance of Automobile Manufacturers, a Washington-based trade group. A spokesman for the Alliance said research on rollover crashes is under way and the group could not comment before the research is complete later this year.
Case files in the National Accident Sampling System, the government’s database of in-depth crash investigations, show numerous models on the roads today can collapse in crashes of less intensity than the Volvo test crash, said Carl Nash, a former director of strategic planning at NHTSA who now consults on roof-crush lawsuits. The damage is especially severe if a roof impacts the ground a second time, he said.
"It’s a clear safety problem," Nash said. "It’s absolutely, abundantly clear."
Test margins in question
Ken Digges, director of a rollover research project at George Washington University, said roofs that pass the 216 test may totally collapse at slightly greater forces. The test does not provide for an adequate safety margin for overloads or repeated roof impacts, he said.
"You can meet the test, but if you increase the load the roof can totally collapse," Digges said. "I suspect 216 has driven design the wrong way."
While Detroit’s automakers contend there’s no cause-and-effect relationship between crushing roofs and injuries, they have touted the importance of a strong, secure structure in advertisement for decades.
In March, GM ran newspaper ads touting the use of "light-weight, ultra-high-strength steel" in its new Cadillac SRX sport utility vehicle.
"A stiff structure contributes to a secure cabin," the ad stated. "This high-strength steel team of bodyguards provides a formidable defense for driver and passengers alike."
That echoes an ad Ford ran for its 1964 Country Squire station wagon touting a roof strong enough to hold the weight of nine kids.
"Take the roof these youngsters are perched on. Three separate steel braces make it super-solid to sit on" or ride under, the ad stated.
Automakers often explain roof-crush injuries by arguing that no vehicle design can stand up to the most violent rollover crashes. The basic principles that are applied in passenger car safety can be seen on an extreme scale on the NASCAR racing circuit.
NASCAR employs roll cages, 5-point seat belts and helmets to reduce injury risk. There are important differences between racing cars and passenger vehicles. But the racing experience shows that even dramatic high-speed rollovers are survivable with the proper protection.
Scott McClellan is executive vice president of Independent Witness, a Salt Lake City safety research firm that has been equipping NASCAR vehicles with safety instrumentation for the past 2 1/2 years.
"I can’t recall a rollover or flip that resulted in a serious injury," McClellan said. "If the occupant compartment integrity is maintained, the potential for injury is pretty low."