Ridecamp: [RC] Trailer accidents/to tie or not

I have a friend that told me that every trailer accident that he has seen,  including his own roll-over, tied horse died due to broken necks and the loose horses for the most part survived.  He had a roll-over coming out of Evanston WY with four horses in the trailer.  It was on the freeway at freeway speed.  The horse some how survived the roll over and were running loose on the freeway after he came to a stop.  He will never tie when traveling .I have yet to see the pictures.  I guess they are very spectacular.  Beccy in Ut