A Quantitative Evaluation of the Nighttime Visual Sign Inspection Method

As part of a research project to determine the optimum strategy for sign inspection and replacement in response to pending retroreflectivity requirements, a spreadsheet tool was developed to quantitatively evaluate the effectiveness of different inspection and replacement scenarios. The spreadsheet was designed for yellow and red engineer-grade sign sheetings, and takes into account sign vandalism and knock-downs as well as normal sign aging. The spreadsheet provides estimates of the number of signs in place that would not meet the minimum retroreflectivity standard and the cost of the sign inspection and replacement program. The results from several trials of the spreadsheet show that agencies that generally conform to the key assumptions made to build the spreadsheet should consider replacing all signs every seven years. If total replacement is not possible, an inspection program using retroreflectometers every three years appears very competitive in its effectiveness with a program using typical visual inspection rates each year. The retroreflectometers appear to allow fewer deficient signs, while the typical visual inspection program costs are lower for a given vandalism rate. More conservative visual sign replacement rates do not appear to offer distinct advantages, while typical replacement rates with visual inspections every two or three years allow relatively high numbers of deficient signs to remain on the roads. Other agencies can easily change the parameters of the simulation program to different values in order to evaluate their own scenarios.


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  • Accession Number: 01006297
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 21 2005 11:57PM