I have a feeling this would be considered unacceptable ageism elsewhere, but Japan requires some drivers to display a sticker which indicates to "other drivers that the marked driver is not very skilled, either due to inexperience or old age".
For the Young/New: https://en.wikipedia.org/wiki/Shoshinsha_mark
For the Elderly: https://en.wikipedia.org/wiki/K%C5%8Dreisha_mark