I get you Mark. I think my basic understanding of sub concussive impacts is not clear here, I apologise. I always thought that direct sub concussive impacts to head are more riskier and damaging than those that we get from road bumps. Moreover an athlete or a football player runs aggressively during a play which sends several impacts to his head, faces several violent body to body impacts and falls down many times. The nature of sports is very violent and inhuman so shouldn't that be causing damage more quicker and intense than just travelling in a bus and those bumps slightly shaking our heads back and forth? I hope I am not sounding too stupid here, pardon me if I do. Also I think for those bumps to cause any damage, the road has to be extremely bumpy and rough throughout the journey and the suspension of the vehicle must be in a very poor condition to cause damage to the brain, if any. Otherwise this doesn't make much sense to me if you compare it with the damage caused in a sport like football. My understanding could be wrong altogether here!