The Insurance Institute for Highway Safety (IIHS) has been testing cars' ability to withstand side impacts since 2003, which has led to the introduction of safer cars throughout the years. Now that same test is in need of an update for an interesting reason: cars have become too good for their current test.
"The program has been so successful that the current side ratings no longer help consumers distinguish among vehicles or point the way toward further improvements," an IIHS statement reads.
When everything passes the test, it's time for a higher standard—and one that better reflects today's heavier, more powerful vehicles. IIHS engineers and researchers want to increase the impact speeds and use a heavier movable barrier that more realistically simulates a modern vehicle in a side-impact crash, as the statement explains:
To better reflect the higher-severity crashes occurring in the real world, [IIHS Senior Research Engineer Becky] Mueller and other IIHS engineers began a series of research tests at a higher speed — 37 mph instead of the 31 mph speed used in the current side rating test. They also made the movable barrier heavier, increasing its weight to nearly 4,200 pounds, the average weight of a 2019 model SUV.
"These changes might not sound like a big deal, but the 6 mph speed increase alone produces 42 percent more crash energy," Mueller says. "Together with the weight increase, the modified test configuration has 82 percent more energy than our current side rating test."
The current movable barrier used in the test is just 3,300 lbs—spot-on for a vehicle in 2003, but far lighter than many larger vehicles on the road today.
The current test was formulated in response to the growing popularity of SUVs. The National Highway Traffic Safety Administration (NHTSA) had its own side-impact test, but the movable barrier they used was about the size and height of a conventional car. The IIHS wanted to understand how a collision with a taller SUV or truck would change things.
According to the IIHS, impacts with taller vehicles increased the risk of head injuries in a crash, which you can see in current IIHS tests where the 12-year-old and female dummies' heads are at about the same height as the movable barrier that hits them.
Automakers met this new challenge, going from only one in five vehicles earning a passable rating in the early days of the side-impact test to 99 percent of all cars getting a good rating in the test, the IIHS notes. To do this, they adopted stronger side structures as well as side airbag curtains, even before a federal regulation mandated those airbags.
As such, the IIHS also wants to understand what has worked well in the current test as they tweak and refine it into something a bit more difficult for everyone to pass. While there's no doubt that stronger, safer vehicles have led to fewer deaths, side impacts still caused 23% of passenger vehicle occupant deaths last year, per IIHS statistics.
"This is an opportunity to build on what we've learned in more than 15 years of side testing," Mueller said in an IIHS statement. "We'll update the things that need updating, but we don't need to throw out the things that still work well."
So far, the IIHS performed a new study of real-world side crashes to see how well their test mimics reality. The IIHS explained:
The study included 1999-2016 model year passenger vehicles with standard head-protecting side airbags that had been rated by IIHS for side protection. The researchers looked at the rate of driver deaths per left-side crashes for each model. They compared these rates with 10 specific intrusion and dummy injury measures that go into the ratings, finding that each one was correlated with driver death risk in left-side crashes.
Researchers concluded that every extra centimeter of B-pillar intrusion was a 3% increase in death risk, and each extra millimeter of rib deflection (as measured with crash test dummies in IIHS tests) correlated to a 10% increased death risk.
"This tells us that the current side crash test measures the right things," IIHS Senior Statistician Eric Teoh said in today's statement. "We know that we don't need to go in a completely different direction or upgrade to expensive new dummies as we update the test."
An earlier IIHS study examined vehicles that passed as good under the previous side-impact tests but still led to serious injury or death in a collision. Another test comparing crashes of "good"-rated vehicles with each other compared to crashes with the moving barrier found that SUVs were punching into the cabin area further than the barrier did thanks to the stiff frame rails up front.
Furthermore, the variation in stiffness of the materials in the front of a real vehicle means that it left more of an M-shaped dent, whereas the uniform stiffness of the movable barrier was easier for the vehicle to absorb. These tests are what ultimately led the IIHS to realize that real-world crashes are often more severe than their test and that they needed to rework their barrier as well.
The hope is that automakers will rise to the occasion of this new more difficult crash test, eventually making it obsolete by consistently exceeding the IIHS's new standard. Of all the problems to have, too many cars passing a crash test with flying colors is probably a good one.