Haven' t really been in any. Almost seen one happen but was to early. My cousin and our friend we riding down rails-to-trails(railroad tracks but stripped of their tracks). There was a 5 inch metal pole sticking out of the ground about 2 feet high. Well, he had to straddle the pole and a cement block on the other side going about 40-45 on a Honda Recon. They hit the pole with their back left tire and endoed. My cousin(driver) went of the handle bars and started sliding on his stomach with my 250 lb. friend on top of him and the 4 wheeler on top of that..Well when he got up he had about a 3x4 inch gash in the arm near 1/4-1/2 inch deep. Had to get 8 stiches. Neither one was wearing helmets. Never do, lol. And hell, after that he went mountain boarding with that huge gash in his arm. Didn' t go to the hospital till a few hours after it happened, lol. Total the 4 wheeler. Bent the rear axel. I' ve seen my cousin in some pretty sticky predicaments he probably wouldn' t have been able to get out of if I was there. Like when he flipped it backwards and the 4 wheeler landed on him with the handle bars on his face... He couldn' t move. It was up in some 20 year old trees. Pretty brushy.