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Tesla Model S Fails To Get Top IIHS Crash Rating (usatoday.com)
mrspoonsi writes: Shares in Tesla have plummeted more than 13 percent this week after lower than expected deliveries and the Model S only attaining an acceptable result in recent crash tests. The Insurance Institute for Highway Safety states: "Tesla made changes to the safety belt in vehicles built after January with the intent of reducing the dummy's forward movement. However, when IIHS tested the modified Model S, the same problem occurred, and the rating didn't change. Although the two tested vehicles had identical structure, the second test resulted in greater intrusion into the driver's space because the left front wheel movement wasn't consistent. Maximum intrusion increased from less than 2 inches to 11 inches in the lower part and to 5 inches at the instrument panel in the second test. The first test resulted in a good rating for structural integrity, while the second test resulted in an acceptable structural rating. The two tests' structural ratings were combined, resulting in acceptable structure and an acceptable rating overall for the Model S." A Tesla spokesperson responded to the IIHS's crash rating in a statement to Forbes: "IIHS and dozens of other private industry groups around the world have methods and motivations that suit their own subjective purposes."
There is this saying as old as the auto industry that the most critical safety component of any car is "the nut behind the wheel."
This crash safety tests are fine, and IIHS is trying to make them more fine, but they publish interesting (if not macabre) data on vehicle death rates that don't strictly correlate with the crash-test ratings.
Cheap subcompacts favored by first-time new-car buyers do poorly and two-seat sports cars do even worse. You would think that pickup trucks would do well on account of their bulk and mass, but they don't do as well as you would think, although IIHS found that many aren't that great in their crash tests. Boring sedans do OK and Japanese boring sedans do even better, but nothing tops minivans for not killing people.
These real-world results seem to correlate with driver demographics, with cautious Soccer Moms in their minivans being very safe and other people, not as much.
What drove this home, to excuse a pun, is the time you could buy a Corolla with either a Chevy Nova badge or a Toyota. The Chevy was significantly more dangerous even though it came from the same Fremont, CA plant that later got turned into the Tesla factory. Do you suppose that snobs paying the couple-hundred dollar premium to get a proper Toyota drive more carefully?
The IIHS tests are made by the folks who have to pay out money for insurance claims, and are designed to weed out failure modes they are seeing in actual crashes which led them to pay out more than they were expecting. They made the driver's side overlap tests specifically because they saw it as a weakness with the NHTSA tests. The NHTSA test only covers impacts directly from the front and the side. Yet they were seeing a lot of claims from impacts where cars didn't hit head-on and the intrusion thus bypassed most or all the crash-resistance designed to satisfy the NHTSA test.
Those are the scenarios that the IIHS test is trying to replicate. Passing the "small" version of the overlap test successfully is important because if the car can't, it may actually be better for the driver to let a greater portion of the car's front hit the oncoming vehicle/obstacle, rather than to try to avoid it and only receive a glancing blow. As the size of the impact area shrinks, the stresses on the section receiving the impact increases because there's less material absorbing the same crash energy. So the crash-resistance should be concentrated mostly along the sides, tapering off as you move inwards (perhaps increasing again towards the center). That is what this test is encouraging car designers to do. A car could be designed to let its left or right side completely shear off in a collision which misses the center of the front bumper, and still be completely NHTSA-compliant.