Analysis of Sign Damage and Failure

Abstract

Since the establishment of minimum retroreflectivity levels, agencies and researchers alike have focused on determining the service life of different sheeting type and color combinations. Although deterioration curves and measured retroreflectivity are viable methods for maintaining retroreflectivity compliance, they do not ensure that a traffic sign will convey its intended message. Retroreflectivity efficiency ensures only visibility but does not properly describe the legibility of the sign. In 2011, a data collection effort was conducted by researchers at Utah State University to assess the performance of traffic signs under the Utah Department of Transportation's (DOT) jurisdiction. At its completion, 1,716 traffic signs had been recorded. The researchers determined that the sample sign population was 93% compliant with the minimum retroreflectivity levels. Even though the majority of traffic signs were performing above the minimum retroreflectivity levels, 28% were so damaged that the legibility of the sign could be questioned. Because signs under the Utah DOT's jurisdiction had rates of damage higher than rates of failure, analysis was conducted to determine the contributing factors that led to increased damage rates. Climate and location data were combined with the known location of each traffic sign with the use of geographic information system software. It was determined that average annual precipitation, elevation, seasonal temperature swing, and the exposure of the sign were all contributing factors to higher damage rates.