What do you call these cars used by disabled people, they are everywhere and I've seen them again today and was wondering what they are called; these cars they are very small for a person to sit on used by the disabled for traveling on the sidewalk instead of walking?
In the UK they're called mobility scooters.
The lighter duty devices are often called mobility scooters or just scooters in the US. They fit under the broader category of electric wheelchairs.
Power chair, electric wheelchair, etc. (But not "electric chair" please... that means something else.)
scooter, electric scooter, mobility vehicle, etc.
I think you're talking about electric wheelchairs, also known as powerchairs, EPWs or motorized wheelchairs.
In addition to those names, they are also often called by whatever name their brand is - one example would be "Amigo".