Anything can happen at any time, I wish him a speedy recovery, I know what 5 broken ribs feel like.
I do have one observation, just before the crash as David is well into the cornor, I see the flagman for that end of the track with his back to to David, looks as if he was watching the leader? Life is full of "What ifs" What if David had gone to the inside and struck the flagger from behind? I know you guys run your own rules, but take it from someone who has been there, the flaggers need to be out of the middle of the track, from the outside they can see the complete track, inside you are limited and have to constantly look over your shoulder.
Not trying to be critical here, I just don't want to see anyone else hurt.