I know of two times " release of liability forms" worked..
The first is where a rider was injured during a race and tried to sue the promoter for inadiqate emergency personnel on scene ( lost a kidney and splene)..It went to court and he lost his suit simply for the fact that he signed a relesase of liability waiver to the promoter...It worked then...
The second was, we were at a asphalt short track race in the infield . I had several woman on top of my trailer on the fold up platform..A wheel, tire, brakes caliper and several of the suspension components broke off of a legends car in a bad wreck out of turn 2...The whole mass of bouncing weight jumped the pit wall ,bounced up in the air and hit the rails on the platform of my trailer. It busted through the aluminum like it was not there, knocking two woman to the floor and one of them completly out. It busted her up on the insides some how and knocked her out..It took paramedics 45 minutes to get her off the top of my trailer. Long story short she too tried to sue the promoter and lost simply for the fact she had signed a release of liability to come into the pit area that night and watch the races..
I was a witness and would not testify in her behalf...She knew the risk.