How can football be made less damaging?

There’s a lot in the press these days about the dangers of football (American) and specifically repeated concussions. The game has evolved in the past to deal with too many injuries – the forward pass was football’s way of dealing with Teddy Roosevelt’s ultimatum to reduce injuries. And a lot or rules have been changed to prevent the intentional injuring of quarterbacks.

What rule change would you propose to deal with head injuries?