Minimum sign retroreflective guidelines : summary report

008141021997PDFManualFHWA-RD-97-074RetroreflectivityTraffic control devicesTraffic signsNight visibilityGuidelinesHuman factorsEconomic factorsField studiesMathematical modelsManual on Uniform Traffic Control DevicesUnited StatesUnited States. Federal Highway AdministrationUnited States. Federal Highway AdministrationNTL-SAFETY AND SECURITY-Highway SafetyNTL-OPERATIONS AND TRAFFIC CONTROLS-Traffic Control DevicesIntelligent Transportation Systems Joint Program Office;Federal Highway AdministrationRetroreflective traffic control devices are designed to help offset the lack of visual cues in the nighttime driving environment. Currently, the Manual on Uniform Traffic Control Devices requires that signs be retroreflectorized, but no minimum in-service values are given for the level of retroreflectivity. Due to the degradation of retroreflective materials over the course of years, it is important to have a basis for knowing when to replace signs. A two-phased approach was taken in defining minimum retroreflectivity values for signs. Human factors requirements were considered, as well as economic implications in setting replacement values. This summary report describes the Federal Highway Administration's Computerized Analysis of Retroreflective Traffic Sign (CARTS) model and its use in developing proposed minimum sign retroreflectivity guideline values. Also described are a laboratory study and field evaluation of the values