I have never seen any reference to bike helmets being "rated" for a specific speed or type of impact. Bike helmets are approved based on a single test carried out by the CSPC which is not calibrated to correspond to any particular speed or type of impact. I don't consider the method of testing helmets particularly important to the well-supported fact that these helmets significantly reduce the risk of serious head injury and death.
There are no well-supported "facts" that helmets reduce serious head injury. In fact, among the cycling community, it is a very hot point of contention.
> A 2012 re-analysis of the 16 studies in the Attewell meta-analysis, by Elvik, found that, compared to helmeted cyclists, unhelmeted cyclists were 2.5 times more likely to sustain a brain injury; 2.3 times more likely to sustain a head injury; and 4.3 times more likely to sustain a fatal injury.
https://en.wikipedia.org/wiki/Bicycle_helmet#Science:_measur...
http://www.drianwalker.com/overtaking/
A Google search will reveal other similar studies as well. Wikipedia is not comprehensive.
This is what I term "a small subset of crashes".
Realistically, cyclists ride faster than this. And realistically, the types of collisions you want to protect against are not between you and the ground but rather you and a moving object, such as a car. Bike helmets are not rated for these kinds of crashes.
I would not use the Hovding either. The reason I presented it is because it represents a radically redesigned bike helmet.
Anyhow, as I said before, the only thing you can wear to really prevent bad bike accidents is a motorcycle helmet, which are in fact rated for high speed collisions.