From the fhwa.dot.gov website. About half of traffic fatalities occur at night, although only about one quarter of travel occurs after dark. Although intoxication and fatigue contribute to the high rate of nighttime crashes, nighttime driving is inherently hazardous because of decreased driver visibility.
Adequately maintained retroreflective signs and pavement markings improve highway safety and prevent roadway departure crashes by bouncing light from vehicle headlights back toward the vehicle and the driver’s eyes, making the signs and markings appear brighter and easier to see and read.
Because the retroreflective properties of traffic control devices deteriorate over time, highway agencies need to actively manage the maintenance of signs and pavement markings in order to ensure that they are clearly visible at night.