And, from Peloton Mag (hard to tell if this is independent article or a "featured" (ie paid for) story but it gives the story behind Trek's new helmets):
We hear lots of noise about ‘revolutionary’ new products in cycling. They are essentially never revolutionary, and frequently aren’t even new. But when Trek starts teasing a new product with the tag, “A change like this happens once every 30 years.” We’re pretty sure it’s a big deal. Speculation started. Was the lime green material teased a new frame material? Trek launched OCLV carbon about 30 years ago. But the biggest clue was Bontrager touted the material as well, and it did look a bit like the Koroyd material used in Smith helmets. Now we know. Bontrager is incorporating a new material called WaveCel into its helmets, which it claims is 48x more effective than EPS foam at preventing concussions during unplanned dismounts.
• WaveCel is a collapsible cellular material that reduces the effect of oblique head impacts that generate the rotational forces that can cause so much brain trauma.
• WaveCel is an alternative to the now ubiquitous MIPS layer used by Bontrager in many helmets and most other helmet manufacturers as well.
• According to a study at the Legacy Research Institute in Portland, Oregon, WaveCel is significantly more effective than MIPS in reducing both linear impact forces and rational forces on the brain.
• While similar in appearance to Koroyd used by Smith, Koroyd equipped helmets still use a MIPS layer.
• WaveCel adds a little over 50grams compared to non-WaveCel helmet’s weight.
As most people in cycling now now, its not the blunt impacts we should fear, it’s the oblique, angular impacts at high speed that cause so many concussion as well as life altering traumatic brain injury. Brain cells do not respond well the shearing forces. In the 10-15 milliseconds after an oblique impact it’s crucially important to spread that force out with 10-15mm of movement. If the helmet doesn’t provide that movement, your brain provides it by rotating in your skull. Yeah, that’s as bad as it sounds. Axons connecting brain cells go ‘snap’.