By having specially designed cars that enable them to drive.
Even the ones who by the nature of their disability can’t do anything mentally or visually taxing, like drive, don’t disprove or negate the need for cars because everyone else with disabilities need them to get around. Public transport simply isn’t suitable enough for them.
Even old blind people who can’t pass driving tests use Uber or Lyft, because public transport simply isn’t safe or suitable enough for them, especially during grocery runs.