Driving with a disability that requires a prosthetic arm is a peculiar subject.
1) Speed. Cars may be difficult to drive correctly. They may be more difficult to drive with a disability. With narrow roads, difficult conditions such as darkness, slippery roads or cold temperature they may be even more difficult to drive correctly. Any such difficulty is hugely dependent on the traveling speed. When cutting speed by already 5 km/h, driving may become a lot easier. So one suggestion is to make sure drivers - particularly handicapped drivers - can get a really good understanding about speed, and how much reducing speed can make things better for them. Safety courses can teach you that practically.
2) Car modifications. Our traffic roundabouts are so narrow that trying to steer in, steer around, steer out *and* provide timely indicator lights at the same time just with one hand or with one hand and a prosthetic arm can be a challenge. I can do it easily when I drive around roundabouts at ~ 10-20 km/h, but doing it faster requires trickery and training, experience and freestyling.
At first, the representative of our vehicle registry said I needed a knob with electric buttons on my steering wheel that contains controls for indicator lights, I need power steering and so I was, at first, restricted to modified vehicles with power steering and automatic shifts and a knob with a few buttons on it, for indicator lights and such. This was a bit of a restriction but it makes things extremely safe.
At first, the stump is painful and the prostheses are built to fail.
At first, the prosthetists do their darnedest to motivate you to switch over to myoelectric technology and so they make body powered arms that break every 4 to 10 days or so.
At first, therefore, you need that knob on the steering wheel.
Later, one becomes better and more proficient.
Later, you have coerced the prosthetic technology to comply with your requirement.
Later, prosthetic arms hold up over almost a year when built right. Later, the stump does not hurt a bit when using it, also, to drive, to turn the steering wheel or shift gear on an automatic transmission.
So I went for a re-assessment at the road traffic agency and now I am legally driving cars without steering wheel knob.
3) Car buttons, radio, navigation. It is important to consider that some cars have buttons, or controls, that are a lot easier to use for a particular manual handicap than other cars. I got to the point where I now make that choice, what car or not, also dependent on just how well I can operate the car options. My current car allows me to easily switch ventilation, or rear window wiper, or switch on the radio, whenI wear the prosthetic arm, or also when I do not. I can easily switch the gear for the automatic transmission, which is helpful for steep roads. And the window levers are also easy to reach. Some cars are more difficult with that regard.
4) Prosthetics. Badly built prosthetics can malfunction or jam at any given time.Badly chosen terminal devices can cause a grip to lock to the steering wheel. I find that the right build of a prosthetic arm with a really reliable cable control, and a slanted hook that does not totally lock onto the steering wheel, in combination with a soft cover, provides a great setup for many hours of safe driving.