Some police officers spend their entire shift driving in darkness, and yet don't know the fundamental differences between nighttime and daytime driving. The first major and deadly difference between day and night driving is the accident rate. The night driving accident rate is roughly three times that of daylight driving. The accident rate is a result of much more than simply driving when it's dark. Other factors, such as alcohol and drug abuse, and driver fatigue enter into the nighttime accident rate.
Poor visibility is a part of the big picture.
At night, the driver's normally wide field of vision is narrowed to the field of view illuminated by the vehicle's headlights, the headlights of other vehicles, and any fixed roadway lighting. It should be noted that it is important to keep headlights clean. As much as half of a headlight's total output can be absorbed by dirt on the surface of the light. Keeping headlights clean is especially important in winter, when they are frequently covered with road dirt and encrusted with salt. Likewise, a clean windshield is a vital part of safe nighttime driving.