Don't know the specific answer to your questions. i did a little research online and found a website that may be of help. You can call them and ask for more info and perhaps they refer you to the an agency that can help. Good luck.
Check with your local VA. Ours has a volunteer Veterans Transportation service. It's free to veterans enrolled for VA healthcare. Also here our local council on aging offers extremely low-cost transportation to medical appointments ($5.00 round trip).
h-gac.com/human-services/aging/senior-center-services.aspx