Imagine being in a situation where your car has gone off the road and into a lake or a pond, you're conscious, but the vehicle is going underwater.
You stay calm, go to reach for your little neon-orange window hammer, and swing at the glass of your driver's side window. The glass cracks, but doesn't break. You swing again, but still, nothing shatters. It's too late to open the door, you're stuck.
Not only is that a terrifying scenario but according to a study released Tuesday by AAA, it could be a more common one than you think. Part of the reason for that is that many cars on sale today no longer have tempered glass side windows, having switched to laminated glass for safety reasons (we'll explain more later). The other reason is that some of the glass-breaking tools being sold just don't work as advertised.
Until relatively recently, the majority of glass used in vehicle side windows was just single-layer tempered glass. In case you don't know what tempered glass is, it's been treated to shatter into small granular chunks when broken, rather than jagged shards. It's still the standard for most vehicles, but increasingly manufacturers are switching to laminated glass -- which has been commonly used in windshields for decades -- because of its ability to resist breakage on impact.
This strength is desirable because the federal government found a surprising amount of drivers and passengers being ejected from their vehicles in a crash and changed the vehicle standards to try and reduce that number. If your glass doesn't break, you probably won't go through it.
Unfortunately, the side effect is that in situations where breaking the side window to escape a vehicle is necessary, the laminated glass is proving too resistant. It's a trade-off though. The types of crashes which the government changed the regulations for are more common than people driving off the road into the water.
So if you have laminated side windows, what can you do? Well, according to the AAA study, your rear side windows may still be made of tempered glass, but you should find out if that's the case before you're trying to escape your vehicle. Otherwise, you need to try and roll your window down as quickly as possible before water pressure makes that impossible.
OK, so your car doesn't have laminated glass side windows, cool -- but now you have to decide which emergency tool to get and keep in your glovebox. You'll generally have two choices, the first is the very common hammer type. These devices are usually small and made mostly of brightly-colored plastic. They have a pointed steel end on the hammer face meant to help crack the glass.
The other type uses a spring-loaded pin that you press to the glass to break it. This type is great because it's not relying on you being able to swing a hammer to work and can be wielded by someone who doesn't have much arm strength.
For its study, AAA tested six different emergency tools, three of which were hammer-types and three being spring-loaded. Only four of the six tools were able to break the tempered glass, and none were able to break the laminated glass. It also found that the spring type was more effective more of the time in the tempered glass tests.
So what can you do if your vehicle has laminated glass all around the car? Not much, unfortunately. The good news is that only a fraction of a percent of accidents in the US involve cars becoming submerged in water, so the odds are good that the other inherent protective qualities of laminated glass are going to be a help rather than a hindrance in most crashes.
Volvo Crash Test Lab photos: Crashing cars, saving lives