Field Investigation of Highway Sign Damage Rates and Inspector Accuracy

New federal retroreflectivity requirements present challenges to many state agencies responsible for highway sign replacement and maintenance. This paper describes a simulation model that was developed to provide the North Carolina Department of Transportation (NCDOT) with recommendations to improve its sign inspection and replacement procedures. This research focuses on two key factors built into the model: (a) the rate at which signs are damaged beyond usefulness based on natural or man-made causes; and (b) the accuracy rate of visual sign inspections based on retroreflectivity. The research team conducted nighttime rides with sign inspectors in 5 of 14 NCDOT divisions. During subsequent daytime rides, the team measured sign retroreflectivity to allow estimation of sign deterioration and inspector accuracy rates. Data were collected for white, yellow, red, and green signs and for sheeting Types I and III. Findings showed that approximately 2.37% of inspected signs (per year) were damaged to the point of needing replacement. Findings also showed that inspectors did not reject a large percentage of signs that had retroreflectivity values below the proposed minimum Federal Highway Administration standard. However, rejection rates increased as retroreflectivity decreased. Based on the nighttime rides and daytime inspections, it appears that both damage and retroreflectivity field inspections can simultaneously be conducted at night.

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  • Authors:
    • Immaneni, Venkata Pavan K
    • Rasdorf, William J
    • Hummer, Joseph E
    • Yeom, Chunho
  • Publication Date: 2007-4


  • English

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Filing Info

  • Accession Number: 01050225
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 30 2007 5:21PM