One obvious answer is darkness. Ninety percent of a driver's reaction depends on vision, and vision is severely limited at night. Depth perception, color recognition, peripheral vision are compromised after sundown. Older drivers have even greater difficulties seeing at night. Another factor adding danger to night driving is fatigue.
Drowsiness makes driving more difficult by dulling concentration and slowing reaction time.
Alcohol is a leading factor in fatal traffic crashes, playing a part in about half of all motor vehicle-related deaths. That makes weekend nights more dangerous. More fatal crashes take place on weekend nights than at any other time in the week. Fortunately, you can take several effective measures to minimize these after-dark dangers by preparing your car and following special guidelines while you drive. Have your headlights properly aimed.