As aabeck states, rides usually come under the jurisdiction of a state inspector in the US. The worst are the fair rides that get put up and taken down every week. Appears there are cursory inspections and the inspectors rely on the operators. Two fairly recent incidents around me are a boy being electrocuted because of a ground fault on an ungrounded ride and the mechanical failure where a set of carschairs came flying off the ride due to rusting. If standard design practices were followed, then you can imagine how much of the structure had to be eaten away for the failure to happen. I guess no one was looking at that or no one cared.