I was part of a team in uni who worked with a state park to develop a plan for one of these and this was one of the biggest concerns for us. We ended up deciding that it was a self-selecting process anyway. Speaking candidly, very few obese people have any interest in going outdoors and it’s not like these chairs are super comfy or easy to ride. The people who take the initiative to schedule one and go through the orientation/training process probably have valid reasons for needing the chair and are most likely motivated to go outdoors, as well. It’s been a few years since I talked to the park ranger we worked with, but it seemed like that was there hadn’t really been any issues w/r/t your concerns.