If you think about it, in principle, the best you could do is make a device that 1) controls the acceleration of the head assuming it will reach a certain displacement e.g. d=10cm with final velocity v=0 ) transfers the forces from the skull to elsewhere.<p>So the absolute best protection you could get would be some kind of cage around the head not linked to the head at all -- maybe you couple this cage directly to a vest akin the HANS device you mentioned, and actuate a separate mechanism smoothing the head movement, with the largest radius possible around the head to provide the least maximum acceleration ( a_maxmin = initial velocity^2 &#x2F; 2 * d ). Normal head movement could be completely unhindered.<p>Now since this is a sport this could devolve into a bunch of people just bashing pieces of plastic into each other, which may or may not be desirable over the current situation; how much such a device would cost (not accessible to amateurs); and as others mentioned it&#x27;s also possible their velocities will increase to compensate, maybe not changing the number of injuries at all.