Would like to add to the above comment. Trikes come in all kinds of configurations, from adult trikes which are sometimes called "Granny" trikes, to semi-recumbent step-through type trikes, to fully recumbent trikes. All of them can have electric motors added to them, but the basic problem is to decide whether they can be easily mounted or controlled by the physically impaired rider. And here comes into play the height of the seat and the ability to lift one's legs high enough to place them on both sides of the trike. And at this point comes the need to decide whether the so-called "tadpole" or "Delta"trike would best fit one's needs. The cautions of "Rich C" apply here, for a fall or tumble for an already physically impaired individual can have tragic consequences, as could also be the case with an elderly person who might find themselves unable to control the extra power provided by an e-assist motor.
Court has indeed given thorough reviews of many of these trikes. I, myself, have spinal stenosis and settled on an "adult trike"--the German Made PFIFF Comfort Trike with an e-assist motor. After a few days of getting used to it, I found it very easy to control, given a good understanding of how to balance it. I've never been anywhere close to capsizing it--you just have to remember how you rode one when you were a kid, and not try to move your body with it as you would with a diamond frame bike. There are indeed, certain trike manufacturers who specialize in making add-ons specifically made to help the physically handicapped person get back outdoors on a trike.
On my part, faced with the predicament of finding some means of mobility when I could no longer drive an auto I launched into a personal search for mobility alternative which finally turned into a book. It's called "Keep on Moving! An Old Fellow's Journey Into the World of Rollators, Mobile Scooters, Recumbent Trikes, Adult Trikes, and Electric Bikes." The section of Electric Bikes draws heavily on the pioneering work of Court and contributors both to this site and to Bentrider Online. Hope this helps.