I told you an outside factor related to the guest - such as obsesity - would be one of the lead contributing factors.
I'm going to ruffle some feathers here, but I'll come right out with it.
Parks should, under the law, have the right to refuse anyone of exceptional size and/or physical handicap to ride. ADA regulations have reached a ridiculous fever pitch, and those that are obsese are developing a mentality that "what everyone else can do, I should be allowed to do." Sorry, but that's crap. They should NOT be allowed to do something that could compromise their safety. A park should be protected, just as any citizen is, should they refuse a person. If I have a backyard pool with a slide, I can - by law - refuse someone access to it for fear their physical limitation would endanger them should they go on the slide. However if a park does such, it's considered discrimination, and the ADA gives the guest the right to sue.
It's a fact of life that those of larger proportions simply cannot do, or should not do, things that would be impeded by size. By living in a "PC" society, we are perpetuating myths. By "pretending" that a person of extreme size or limitation is completely able-bodied endangers them. It generates a mentality, in cases such as coaster riding, that they are superior to a mechanical device.
It's lose-lose for the parks. If they refuse the rider - they get sued. If they allow the rider - they run the risk of getting sued should any accident (no matter how small) occurr.
When I worked on Beast crew, there was a fellow who came with his Dad to KI every weekend and rode The Beast. He was middle-aged, wheelchair bound and LOVED KI. I really appreciated his love of the park. However, he was handicapped to the point that he could not lift or manuever himself out of his chair or into the train whatsoever. As a matter of fact, (as I recall) his arms had very limited mobility and he was not able to hold the lap bar properly. (I believe, he had Cerebral Palsy to the point that he was constricted to the chair) We'd have to hold the trains while three of us lifted him from his chair onto the ride. We then had to adhere him to the seat with a special torso strap and click his lapbar down on him. This was AFTER we had notified those that had waited in line (he didn't have to - came up the exit) that he would be riding in front of them for the next two circuits (he was permitted two consecutive rides.) We'd send him on his way, and every single time I'd pray to God that he came back in one piece. I stayed scared to death something would happen and I'd be responsible. However, by law, I was not allowed to refuse this. But also, had something happened, my neck was on the chopping block for blame. Now I was in my late 20's - and working at KI for kicks. Most employees at KI are teens - or young 20s. That's an immense responsibility to place on "a kid." Yet, had I refused to allow him - or even refused to assist him - I would have been fired and the park sued.
Now I ask... is that fair to anyone? Him? Me? The park?