The ability to change focus declines with age. Younger drivers need only about two seconds to adjust their focus from near to far, such as when looking from the speedometer to the road. Drivers over 40 take three seconds or more with more time needed with increasing age. The eye's lenses grow thicker, pupils shrink and muscles lose elasticity with age, making older drivers much more sensitive to glare. Colors become harder to see, especially red, as we age.
Some older drivers take twice as long to distinguish a flash of brake lights as younger drivers.
Peripheral vision narrows with age and depth perception affects the ability to judge how fast other cars are moving.