Therapeutic horse riding is generally not used as a form of travel, and because it is a therapy riders are usually accompanied, so I don’t know if you’ll find much information on how people with disabilities could ride unassisted while researching that, but I’d encourage you to look into the sport of Para-equestrian. It’s an event in the Paralympics. There are some organizations for para-equestrians, though I don’t know how much actual information their websites have about the logistics of it, because everyone’s disability is unique and so their needs when it comes to how they ride would be different. Here’s a couple of the websites:
- United States Para-Equestrian Association
- International Federation for Equestrian Sports
- Riding for the Disabled Association
You might also want to look into equipment para-equestrians use, because you could likely figure out how to modify them to fit the animal you’re using in your story. Here are just a few I found:
- Para-Equestrian Products (This site is run by a para-equestrian with cerebral palsy, and she also writes about her experiences as a para-equestrian.)
- Saddle Modifications for Para-Equestrians
- Disabled Sports USA
- Riding for the Disabled Association - Special Equipment Guide
There are also several para-equestrians who have blogs, and you should definitely look at those, so you can get a better image of disabled riders as a whole. A few I found:
I should note that both therapeutic horse riding and para-equestrians are not always physically disabled. Many are mentally and/or developmentally disabled, and so the information I’ve given you pertains to all disabled people who participate in para-equestrian.