2013 Session: 805

• Measurement Bias and Reproducibility of In-Service Sign Retroreflectivity Readings Made with Handheld Instruments
  Abstract: With new requirements to maintain sign retroreflectivity, a number of agencies have selected maintenance programs that involve measuring retroreflectance of traffic signs. The accuracy and precision of handheld retroreflectometers, however, is not regulated, and the bias and reproducibility of handheld retroreflectometers needs to be assessed. This had, until now, not been done for instruments on in-service signs in field conditions.To assess the measurement bias and reproducibility of handheld retroreflectometers, readings of sign retroreflectance were taken during two periods separated by a 3-week interval, each time by two retroreflectometers. The average measurement bias was found to be 1.59 and 20.0 cd/lx/m2 for readings made on beaded and prismatic signs, respectively, and the reproducibility error was found to be 1.66 and 11.9 cd/lx/m2 for readings made on beaded and prismatic signs, respectively. When compared to the total retroreflectance of these signs, these average differences are relatively small. However, the amount of observed variability is enough to conclude that supplemental readings, whether by another instrument or at a different time, may produce markedly different values of retroreflectance.
  Authors: Brimley, Bradford; Carlson, Paul J.; Ye, Fan
  Authors: Brimley, Bradford; Carlson, Paul J.; Ye, Fan
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Operations and Traffic Management
  Session: 805
  Paper Number: 13-0032
• Current State of Research on the Long-Term Deterioration of Traffic Signs
  Abstract: The minimum retroreflectivity standard for traffic signs in the Manual on Uniform Traffic Control Devices requires that transportation agencies replace signs when they deteriorate beyond a prescribed minimum level of retroreflectivity. There are many sheeting products available with a variety of initial retroreflectivity levels for agencies to choose from when they need to install signs, but one primary concern agencies may have is their expected life. This paper serves as a compilation of studies related to the long-term deterioration of traffic signs to present what research has been completed in this area. The research compiled here shows that some signs may have an unrealistically long expected lifespan, a conclusion resulting from limitations in the study designs and their assumptions. A controlled long-term study of the deterioration of traffic signs with respect to retroreflectivity and color is encouraged to provide agencies the information necessary to select appropriate traffic sign products.
  Authors: Brimley, Bradford; Carlson, Paul J.
  Authors: Brimley, Bradford; Carlson, Paul J.
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Operations and Traffic Management
  Session: 805
  Paper Number: 13-0033
• Analysis of Sign Damage and Failure: Utah Case Study
  Abstract: Since the establishment of minimum retroreflectivity levels, agencies and researchers have focused on determining the service life of different sheeting type and color combinations. While deterioration curves and measured retroreflectivity are viable methods for maintaining retroreflectivity compliance they do not ensure the ability of the traffic sign to convey its intended message. Retroreflectivity efficiency only ensures 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 (UDOT) jurisdiction. At its completion, 1,716 traffic signs were recorded. The researchers determined that the sample sign population was 93 percent compliant with the minimum retroreflectivity levels. Even though the majority of traffic signs were performing above the minimum retroreflectivity levels, 28 percent were damaged to the degree that the legibility of the sign could be questioned. Since signs under UDOTs jurisdiction had higher rates of damage than rates of failure, analysis was conducted to determine the contributing factors that lead to increased damage rates. Climate and location data were combined with the known location of each traffic signs using 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.
  Authors: Boggs, Wesley Bill; Heaslip, Kevin; Louisell, William
  Authors: Boggs, Wesley Bill; Heaslip, Kevin; Louisell, William
  Year: 2013
  Document Type: Paper
  Subject: Maintenance and Preservation; Operations and Traffic Management
  Session: 805
  Paper Number: 13-4054
  Practice-Ready: Yes
• Measurement Bias and Reproducibility of In-Service Sign Retroreflectivity Readings Made with Handheld Instruments
  Authors: Brimley, Bradford
  Authors: Brimley, Bradford
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Operations and Traffic Management
  Session: 805
  Paper Number: 13-0032
• Current State of Research on the Long-Term Deterioration of Traffic Signs
  Authors: Brimley, Bradford
  Authors: Brimley, Bradford
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Operations and Traffic Management
  Session: 805
  Paper Number: 13-0033
• Analysis of Sign Damage and Failure: Utah Case Study
  Authors: Heaslip, Kevin
  Authors: Heaslip, Kevin
  Year: 2013
  Document Type: Presentation
  Subject: Maintenance and Preservation; Operations and Traffic Management
  Session: 805
  Paper Number: 13-4054