Only one-third of all driving is done after dark, but two-thirds of all fatal accidents happen then.
The major problem associated with nighttime driving is limited visibility. With only your headlights to show your way, you are boxed into a virtual area that extends only about 300 feet in front of you. If an object ahead is a dark color or does not reflect your headlights, you may not see it until it is too late.
In addition, your eyes get fatigued by continually adjusting to rapidly changing distances and conditions. Drivers cannot judge distances as well when it is dark. Objects that, in daylight, help you relate to other objects cannot always be seen at night.
The other factor is that there is more alcohol consumption in the nighttime as opposed to daylight hours. Even drivers who are not legally drunk, but have consumed only a few alcoholic drinks, may have their reflexes slowed just enough to not be able to react to the actions of other drivers or a hazard on the road.