Abstract
The visual information provided by road signs gives the motorist fundamental instructions governing the selection of routes, safety at intersections, warning of physical obstructions, and delineation of a safe path for travel. This report covers those retroreflective signs dependent on headlamps illumination and provides information on the replacement point for retroreflective signs degraded from the effects of weathering. If sign replacement is not necessitated by any other cause, and eventual loss of nighttime luminance and visibility will result from the effects of weathering.