I have to agree with Soren on this. The DOT standard is basically a "Minimum Performance Spec", which when adhered to or tested to, should, in most circumstances, prevent head injuries. There are the equivalent of this type of Specification in every facet of our lives, in Germany, it's the DIN and TüV, which sets the minimum standard for ALL kinds of stuff, with regards to not only performance, but also standardisation, so that if I buy a Fastener or Connector that is DIN 912 for instance, from any supplier, it will work interchangably and up to a certain load rating in my application. Same goes for SAE here in the states, JASO in Japan, and CE in Europe. It is not intended to say "if you meet DOT, then it is perfect", but rather, sets the same bar for everyone to reach, but it is a MINIMUM bar. Snell was supposed to improve upon that, and some manufacuturers meet both, the idea being that if you also meet Snell, you not only meet the bare minimum required by NHTSA, but some higher performance level, and so are somewhat safer. They test with different methods to different levels, so are not exactly an apples to apples comparison. SO, don't take a DOT as a guarantee of performance or safety, because it isn't, it is a guideline, like OSHA, for trying to design better and safer products, based on a series of tests and their results. Are those results indicative of the real world. Maybe the real world with regard to some situations, but not all. There are always accidents that have circumstances no one can predict or test for. We are required all the time by our customers to test really outlandish circumstances, that we feel are not really applicable to the real world, and when we protest, or suggest alternatives, they have some test engineer who will say "Oh, this is what our data shows" or "this is what we feel will cause a failure in our vehicles" and totally disregard our experience.
