Colors, especially red, become harder to see with age. Some older drivers take twice as long as younger drivers to recognize the flash of brake lights. Other common age-related deficits include eye muscle dysfunction, which impairs the ability to scan the driving environment, and poor contrast sensitivity, which can make it hard to detect curves in the road, see a gray vehicle at an intersection or a pedestrian at a crosswalk or see clearly in bad weather. According to the AAA Foundation for Traffic Safety, the amount of light needed to drive doubles about every 13 years. Few people over 65 need to be told that with advancing age joints tend to stiffen, making it more difficult to turn one's head when pulling out of a parking area or when backing up.
Muscles gradually weaken, and that weakening can impair a person's ability to steer and brake.
Reaction time slows, increasing the response time when faced with any sort of road hazard, especially a vehicle that suddenly stops or turns in front of you. Hearing deficits common in older people can affect their ability to detect and respond appropriately to the sirens of emergency vehicles, railroad crossing signals and the warning horns of other drivers. Your mind may be as sharp, but it works more slowly as you get older. Older drivers also are more easily distracted by noise or other disturbances, including the radio and the conversation of others in the car. Then there are a host of disorders that become increasingly common with age that can further limit ability to handle a motor vehicle safely.