Factors Affecting Sign Retroreflectivity

This study was undertaken to better understand the factors that may affect road sign retroreflectivity, specifically age and physical orientation. A better understanding of these factors could provide guidance to ODOT in managing its inventory of road signs. The findings showed that over a twelve-year age span, most sign retroreflectivity readings were above the minimum ODOT standard. Retroreflectivity did not vary predictably with age. There was some evidence that retroreflectivity may be affected by sign orientation (direction facing), due to the weathering effects of windblown dust and precipitation. Additional data collection in more severe climates of Oregon might provide more evidence to support this finding. The report includes recommendations for further study and for record keeping in the ODOT sign maintenance program to provide a larger body of data.