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Publication Number: FHWA-HRT-07-042
Date: April 2007

Maintaining Traffic Sign Retroreflectivity: Impacts on State and Local Agencies

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Appendix B - Summary of Reported Impacts

Agency/Location Reported Impacts Comments Implications
NCHRP 346 (7)
  • Low level criteria will have minor impact over a 10 year implementation.
  • Many agencies have implemented sign management processes.
  • Cost model can be useful to assess impacts over differing sign system conditions.
  • The low level criteria evaluated used values similar to those most recently proposed.
  • The cost factors used in the analysis reflect costs for that time period.
  • Some costs have gone down, few materials included.
  • Based upon a broadly gathered sample of signs.
  • Overhead and street name signs not addressed.
  • Minor impact conclusion.
  • Concluded that impact costs should not include process improvement costs.
  • Supports long term implementation to minimize costs to agencies.
  • Cites need for research on field methods, degradation rates, and liability issues.
USDOT Highway Safety Evaluations (14)
  • Sign projects are among the highest payoff safety projects based upon evaluation reports submitted between 1978 and 1996.
  • B/C ratio for sign projects 22.4 to 1.
  • Conclusions based upon several years of data, but reporting process was not uniform.
  • The data does not isolate the nature of sign improvements, so the relation to nighttime visibility cannot be determined.
  • Evidence that improved signing reduces crashes leading to a highly positive safety benefit.
Texas DOT (8)
  • Texas DOT sign crews reviewing 50 signs in training program suggested replacement of more signs than might be necessary under the proposed FHWA minimum requirements.
  • Findings raised questions about the appropriateness of the contrast ratio aspect of the requirements.
  • The AASHTO Task Force participated in these exercises and similarly found the need to replace about three times more signs than would needed to satisfy the minimum levels.
  • Usefulness of the visual inspections method led to the proposal that agencies be allowed to use it instead of measurement methods.
  • TF agreed that it may be appropriate to alter the contrast criteria.
  • The results suggest that the minimum values will not affect agencies as much as might be expected.
  • The field exercises demonstrated the value of night inspections to find a multitude of possible problems that adversely affect night visibility.
FHWA Impacts Report (5)
  • Nineteen agencies provided feedback on survey about sign management efforts in State & local agencies.
  • They provided feedback on the expected impacts of the new requirements.
  • Seven of these agencies provided data for a sample of their signs that was used to estimate overall impacts.
  • Estimates of the impact led to the conclusion that the requirement would not have major impacts if implemented over a long period.
  • Impacts analyses based upon estimates of the number of signs based on a small sample.
  • The sample was obtained from agencies who volunteered to provide the data leading to possible bias.
  • The minimum levels considered were similar to the most recently proposed levels.
  • Survey feedback indicated a widespread range of perceived impacts and highly variable costs.
  • This study added evidence that the impacts of the requirements would be minor.
  • The range of perceived costs is great. Efforts may be needed to assist agencies in estimating more specifically their costs.
Indiana DOT (9)
  • Retroreflectivity was field measured for a sample of signs in five parts of the State.
  • Data indicated that more than 90% of the signs met or exceeded the minimum levels proposed by FHWA in 1998.
  • Data analysis found no effect for cleaning of signs before measurement and no effect associated with differences in environmental factors in different parts of the State.
  • Recommendation to the State to increase the replacement cycle for all but stop signs to 12 years.
  • The data collection did follow ASTM procedures, but it is not believed that this had an impact on the conclusions.
  • The agency only uses Type II material, so the results are less generally applicable.
  • Impacts of new requirements considered low.
  • Good example of how data can be used to justify extending replacement cycle.
  • Useful insights on wiping effects that can be included in the procedures.
Mendocino, CA (15)
  • Road safety reviews which focused on sign and markings led to crash reductions savings in excess of $11 million.
  • B/C ratio of 1:159 reported.
  • Program cost were approximately $160,000, but calculated crash savings ranged from $12.8 to $23.7 million.
  • This study relied on CHP data which covered a ten year period.
  • There was a limited number of sections, but the safety experience of State roads in the area were used as a control.
  • The effects of signing and marking improvements was not isolated.
  • Some skepticism is needed relative to the order of magnitude of the benefits, but it there would seem to be ample evidence of the value of good delineation and signing.
  • Detailed of the review process and reasons for 3 year frequency should be pursued.
North Carolina DOT (11)
  • The agency undertook an extensive analysis of current sign practices and options available.
  • It was estimated that there are over 3.2 million signs on the streets and highways in the States.
  • Estimates of sign condition were generated from sample studies. Less than 10% of the State’s signs were believed to be below the minimum levels.
  • The State already conducts regular night sign inspections.
  • After considering a broad range of alternatives, it was recommended that the State undertake a comprehensive sign inventory and develop a full-function SIMS. Price over $4 million.
  • The report contains a good summary of information on sign inventory and management systems.
  • A lot of options considered in the development of NCDOT strategy.
  • Useful critiques of estimating tools.
  • Good long-term life-cycle cost analyses.
  • Recommendations suggest a large impact on the State, but the bulk of the costs are associated with putting a comprehensive SIMS in place.
  • Less than 10% of their signs estimated to need replacement.

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