By now, most drivers know how dangerous rollovers are. According to the National Highway Traffic Safety Administration, they make up only 3% of all accidents, but account for 31% percent of all traffic vehicular fatalities.

One reason rollovers are so dangerous is that, when a vehicle rolls over, its roof can crush down on the occupants, causing head injuries, paraplegia and death.

Windshields Keep the Roof Up

The surprise is that, in today’s vehicles, the windshield is engineered to provide much of the stiffness necessary to keep the roof from collapsing.  In fact, some experts say that the windshield accounts for up to 60% of the cabin’s structural integrity in a rollover.

If It Isn’t Installed Right, It Won’t Stay In

If the windshield pops out of the frame in a rollover accident, it can’t do its job of holding the roof up. Sometimes, an improperly installed windshield will pop out on the first roll, allowing the roof to crush down on the second. That’s why, when someone is killed in a rollover that should have been survivable, experienced accident investigators want to know about the windshield: Did it stay in the frame as it was supposed to? Or did it pop out? If it popped out, was it the factory original windshield or had the windshield been replaced at some point after the vehicle left the factory?

Because of the demands on the windshield, field replacement of a cracked or broken windshield has become a tricky procedure. For example, if an installer doesn’t wear disposable gloves when handling the replacement windshield, oils from his hands can contaminate the bonding surface. The process of "gluing" the windshield into place is also critical. Even if everything else is done right, the bond’s strength can be compromised if the car is left outside in the sun with the windows rolled up. Or if the car’s owner is allowed to drive off with the car too soon. Any resulting imperfection in the bond will allow the windshield to pop out in an accident.

The Danger Is Real

The National Glass Association has studied NHTSA’s crash data. It won’t say exactly how many of the deaths in NHTSA’s database resulted from improper windshield installation, but it concedes that "a measurable percentage of those fatalities occur when an improperly replaced windshield does not remain firmly bonded to the vehicle during a crash."

Of course, consumers are not in a position to inspect a windshield bond, or to otherwise ensure that the installation was done right.  But the expert installers know how important the job is, and they are supposed to get it right. There’s no question that, because of the way today’s cars are designed, it can mean the difference between life and death.