Cooley On Cars
Smarter Driver: New innovations in roof designThe roof of your car is mostly a place to mount the sunroof, but it's in the middle of a technology revolution that makes it a major piece of safety tech.
Now, two major good things happen when your roof is strong and stays intact. First of all, the roof doesn't intrude and injure passengers or kill them inside the vehicle. But secondly, the belt, the airbags, the windows, and the windshield have a strong base so they can stay in place and do their job keeping you from leaving the car which is a big problem in rollovers. Only about 2 percent of the nation's roughly 9 million annual car accidents are rollovers, but they typically account for an astonishing 33 percent of fatalities. So, say hello to a tougher roof standard. Now, new federal standards for roof rollover strength were passed in 2009. They started phasing in September of 2012 and full phase-in across the entire fleet of new vehicles sold in the U.S. as of 2017 model year cars. Now, before these new standards had kicked in 2012, we go back to 1973 for the last time roof crush specs were set, and back then, the federal standard was only that it had to withstand one and a half times the weight of the vehicle. Today, that's a poor rating. That would not even be a passing grade. Now, the Insurance Institute for Highway Safety awards those coveted rollover standards based on a test where they come right here with a big machine that tries to deflect this part of the roof, 5 inches total deflection. The question is, "How much weight does it take?" That's where they come up with a ratio based on the car's weight. To get a good rating, which is the best, there has to be a 4:1 ratio. In other words, the roof can support four times the car's weight of an impact. Now, there are some downsides to all these additional roof strength performance, a couple trivial ones, and that is, there's an estimate that it costs maybe $54 more in your car's MSRP to create all this stronger structure and $16 to $62 in additional fuel consumption due to some added weight. Those are small numbers, but there is a bigger concern. And that is this. As these pillars get stronger, they're getting thicker. Add to that, the airbags that are in them, the padding here for federal head-impact standards, and the increasing slope for aerodynamics, and you've got a visibility problem. University of Michigan did a study that found these increasingly thick pillar designs make invisible for a substantial time a pedestrian who could be in your path during a typical left turn at an intersection, let's say. In the EU, such outward visibility is regulated. In the U.S., it's not. The IIHS has roof-crush ratings by car model on its site, and since these new standards are being phased in, it pays to double check. So, bottom-line, when you look at your car next time and see the roof and the pillars and think you're just seeing something that keep the rain out and keep the glass in place, you're looking at some pretty serious engineering that has come a long way in a few years toward saving your life.