1. Discomfort or nervousness while driving.
  2. Dents and scrapes on the car or the fences, mailboxes, garage doors and other surfaces around the driveway.
  3. Difficulty staying in one lane.
  4. Getting lost.
  5. Difficulty paying attention to road signs, road markings and traffic signals.
  6. Response time is slowed.
  7. Medical conditions that affect one’s ability to handle the car.
  8. Recurrent close calls.
  9. Trouble judging gaps in traffic.
  10. Being honked at frequently or becoming angry at other drivers (which could probably describe most drivers in any American big city).
  11. Other people not wanting to ride with the person.
  12. Inability to see both sides of the road while looking straight ahead.
  13. Difficulty keeping concentration on the road.
  14. Having a hard time checking over one’s shoulder to back up or change lanes.
  15. Frequent tickets or warnings from law enforcement.

Source: AARP