Zip-lines. They are being installed in private recreation parks and even public parks all over the world. The physics is pretty simple. The cable is essentially a ramp on an decline. Gravity down force helps to translate your potential energy into kinetic energy. Frictional resistance on the cable and some air resistance on your body will limit your speed. Down you go. Fun huh? What happens if the zip-line goes down too, while you are on the line? What happens if the zip-line operator's equipment fails? If they are found to have failed to test and repair then you can sue for your medical bills, right? Wrong! You're screwed. Here is why.
It turns out that you have signed a waiver form, at the top and bottom of the form, which says that for the privilege of riding the zip-line or other thrill ride, you choose at that time to give up any right to sue the operator of the ride. Oops.
Surely, you think this will not stand up in a court of law if evidence shows the operator was responsible for your accident, right? Wrong again. Courts around the US and Canada are declaring the waivers binding and protecting from the ability to sue for your injuries. You can read an example of this at the Lexology website. (Click Here)
So. I have never zip-lined and will never do so if I have to sign such an agreement. I can do other things like drive cars, pilot or passenger in an airplane and if the manufacturer or operator is negligent, I or my Family can sue them. But, ride a zip-line, go white water rafting, or parasailing and you can be out of luck, severely, if the equipment breaks or you are smashed into rocks, trees or buildings.
Beware the laws of zip-line. They leave you screwed if the physics of zip-line go bad during your ride.