The National Highway Traffic Safety Administration reports that on average, 7,258 people were killed each year from 1992 to 1996 when they were fully or partially ejected from their vehicles in accidents. Two-thirds of those deaths occurred when cars and trucks rolled over several times.
The highest rates of being thrown out of a window--especially a side window--occur in sport-utility vehicles, vans and pickup trucks. With cars, such an event is half as likely. In 1996, more than half of all deaths caused by ejection from a vehicle involved sport-utilities.
"SUVs tend to be involved in a disproportionate number of rollovers, and ejections are related to rollovers," said Stephen Summers, a NHTSA engineer who is part of a team researching how glazing side windows with special plastics might decrease the number of fatalities from ejections in all kinds of vehicles.
To put this more graphically, regulators are looking at what they can do to prevent people from dying when their sport-utes--and other types of vehicles--roll over in accidents and bodies, or limbs, fly through the front and rear side windows after the glass shatters into tiny pieces. About 98 percent of people injured in such accidents were not wearing their seat belts, and many of them died from head injuries.
NHTSA said the problem has taken on more urgency as sport-utility vehicles and trucks, which have a higher center of gravity and thus can flip more easily, have become increasingly popular with consumers. This has caused researchers to focus on how to prevent injuries in sport-utility and light-truck accidents.
For six years, the agency has been studying what its engineers call "ejection mitigation"--or how to keep people inside their vehicles in accidents. Seat belts are a big help, as are various types of glass that don't shatter easily and that absorb some of the energy from a crash.
NHTSA is studying several kinds of laminated glass that resemble the type used in windshields. Laminated glass doesn't shatter into tiny pieces; instead it shows cracks or "stars" when it is hit. It also does a decent job of keeping occupants from sailing through the front window.
The rest of the windows in most vehicles are made of tempered glass, which is designed so that, when broken, it shatters into little bits that won't gouge the vehicle's occupants. But it can be broken more easily than laminated glass and does not help hold an occupant in the vehicle.
What researchers have found--and this seems pretty obvious--is that keeping people inside a vehicle dramatically increases their chances of surviving. "Preventing ejections from side windows is one of the few simple things you can do to prevent injuries in a rollover, which is an extremely violent event," Summers said.
But the four types of glazing the agency has been examining with the help of glass companies and outside safety experts present installation and technological challenges.
There are unresolved questions about what kinds of glazing would work best, what kinds of injuries people wearing seat belts would have if their heads hit the window and how much redesign of the door frame would be required. One estimate is it would cost $48 to $80 per car to use glazed side windows, depending on the material used.
Richard Morrison, owner of Glass & Glazing Forensics in Southfield, Mich., said more research has to be done on injuries from "rebound," which refers to what happens when a person's head hits the windows and rebounds backward.
Morrison is worried about increased lacerations, because some of the glazed glass does not fall out of the frame. "There doesn't seem to be a perfect solution," he said.
Some carmakers, such as Volvo and Mercedes-Benz, already offer glazed windows as anti-theft devices.
Volvo markets a $240 glazed-glass option on its S-80 sedan. All four side windows are laminated to prevent "smash and grab," a theft problem that has led to more use of such glass in Europe.
Solutia Inc., in St. Louis, which manufactures plastic used in glazed windows, wants the government to propose a laminated glass standard. NHTSA's current side-window standard focuses on how the tempered glass shatters and the dimensions of the pieces.
"The technology is here today. What we need is a performance standard from NHTSA. It's a little frustrating for us because lives could be saved. Don't delay a good solution to pursue a perfect solution," said Robert Esposito, manager of automotive development for Solutia.
Glass experts who have worked with the agency are skeptical that the research will ever lead to a rule, especially since an increasing number of automakers are offering side air bags, some of which cover the window and offer ejection protection. NHTSA said the two side air bag systems it tested were helpful in preventing people from being thrown out the window.
The easiest solution, everyone on the NHTSA glazing project agreed, is for people to use seat belts.
"This whole ejection thing is a problem of belt use," Summers said. "If we could get 100 percent belt use, it wouldn't be an issue at all."
CAPTION: The laminated windows used in windshields might help keep occupants from being thrown out of side windows, too.