I thought the scariest one was where two riders slide off the track. The tape goes slow-mo just in time for the 1st rider to do a back flip into the padded wall. Just after he hits and starts to fall forward, the second dude's bike flies into the same wall right where his head had just been. Close call.
The one that hurt the most was probably the guy that took an at-speed race bike to the chest while butt-down on the track.
The one that was scary was a side shot of the rider tumbling down the track with the bike behind him summersaulting and spilling fuel then coming to rest and bursting into flames. Must have been a telephoto lens because the rider didn't seem in too big of a hurry to get out of the way.