Closetbiker,
I was only citing the obvious, that weird things do happen. Helmets are not made for this kind of situation, as you have rightly pointed out. Before you posted, I was getting info on the Beaverton bus accident outlined in this thread, which I researched fairly thoroughly:
http://www.bikeforums.net/showthread...t=bus+accident
This is the more likely outcome of a vehicle/cyclist collision with the bicyclist's head under the wheel.
But talking about the helmets cited in the Roseburg situation, and the other one above, it's kinda like trying to break an egg by putting it in your palm, and pushing on the ends rather than the middle. That makes in much harder to break. Things do happen, and sometimes surprises occur.
For all of these accidents, there are multiple causes. Closetbiker focuses on prevention, by staying out of a situation which would produce the accident in the first place. He maintains that with these precautions, the helmet is not necessary, although it is desirable in certain instances.
Closetbiker is adhering to a philosophy that is much like mine, where we have what is called a hierarchy of controls in the safety and industrial hygiene professions. In order, here's the hierarchy:
1. Elimination of the hazard.
2. Substitution of the hazardous substance or situation with a less hazardous alternative.
3. Engineering controls to keep the hazard from the individual.
4. Administrative controls to keep the hazard from the individual.
5. Personal Protective Equipment to protect the individual from the hazard.
Of these, the PPE is the least effective. In the Beaverton, Oregon bus situation (which was a fatal accident), an engineering control needs to be put into place for those who must use that area by bicycle. But there are alternative routes, which would be a substitution of a hazardous situation for a less hazardous situation. However, the hazard needs to be recognized, and kids often lack that ability to recognize the hazards. They may also use "risk compensation" as the study Trombone posted states.
Saying all this, this thread is about bicycle helmets, and that is why I discuss them in isolation to the other types of controls.
John