Which glass is safer in a crash?
Question: My friend was the victim of a smash-and-grab from a brand-new Toyota Camry. The broken window on a rear door shattered in shards. Is safety glass not required on the rear-door windows of cars?
-- Dan Butler,
Answer: The quick answer is that under federal safety rules, all the side and rear windows on a passenger vehicle must be made of tempered glass, but not laminated safety glass. The long answer is that this is part of a huge and complex safety battle.
Modern passenger vehicles contain about 100 pounds of glass, an inherently fragile and dangerous material. A broken beer bottle is often used in bar fights, for example. As far back as the 1930s, auto manufacturers developed laminated safety glass to help prevent injuries when windshields broke.
Modern laminated safety glass has two layers of glass with a plastic film in the middle, making it far stronger and less likely to shatter on impact. It helps prevent passengers from flying through the windshield and road debris flying into the car. The glass is held in place by high-strength adhesives, which also help stiffen the roof in the case of rollover accidents.
Under federal law, all windshields must be made of laminated safety glass.
Laminated safety glass is not required on side and rear windows. Instead, manufacturers can use tempered glass, which breaks into small pieces with fewer sharp edges than regular glass. Tempered glass, which is much stronger than regular glass, is made by heating and rapid cooling during manufacturing.
The Camry uses tempered glass on the side and rear windows, Toyota spokesman Bill Kwong said. If there is any doubt that glass has not shattered properly, the pieces can be returned to a dealer for factory analysis, Kwong said. Tempered glass is supposed to reduce the potential for serious lacerations, though a large number of people still end up cut by glass in accidents.
Laminated safety glass is much stronger than tempered glass, so why not use it in all the windows? The National Highway Traffic Safety Administration has been examining that issue for almost a decade.
Gerald Donaldson, senior research director at Advocates for Highway and Auto Safety, said advanced glazing, either laminated glass or some newer types of material, for side windows would help reduce thousands of deaths every year when passengers are ejected during rollover accidents.
Some luxury vehicles already use laminated safety glass in side windows. Donaldson predicted the federal government will eventually require laminated glass first on motor coaches, saying it began moving in that direction after members of a college baseball team died in a horrific bus crash on a Georgia highway earlier this year.
But in 2002, NHTSA issued a final report that declined to move forward with a new standard mandating laminated glass for all the windows in a vehicle.
Richard Van Iderstine, a consultant and formerly NHTSA’s top expert on vehicle visibility, said that laminated glass is harder and stronger, meaning it would prevent unbelted passengers from being ejected from vehicles during rollovers and other accidents. But it could increase head and neck injuries to passengers who wear seat belts. Federal regulators figured, why increase the risk of injury to people who wear seat belts to help save others who don’t wear belts?
In addition, laminated glass on door windows would require metal frames to stiffen them, much like door windows had in the 1960s. “So, there would be a lot of cost for having that kind of window today,” he said.
There are other problems with stronger side windows. They would tend to trap occupants in cars when they become submerged or during fires, according to Ford Motor spokeswoman Kristen Kinley.
Drownings in vehicles are hardly rare events. Nearly 700 people were killed in the two-year period of 2003 and 2004 in submerged vehicles and another 1,900 were injured, according to NHTSA. The statistics don’t say how many people successfully escaped from a submerged vehicle. When a car falls into the water, an occupant can break a tempered glass window with a sharp object but would find it almost impossible to punch out laminated safety glass.
Emergency rescue experts have also raised concerns about their ability to extract passengers trapped in vehicles with laminated windows, Kinley added. Such arguments are controversial. In 2005, a jury in Zavala County in Texas slammed Ford Motor Co. with a $28-million verdict involving the death of two young people during a rollover accident. Attorneys for the plaintiffs argued that Ford knew that laminated safety glass would help prevent ejection.
Ford argued unsuccessfully that it was meeting all federal rules and regulations. The company settled the case for a reduced amount, Kinley said.