U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
![]() |
This report is an archived publication and may contain dated technical, contact, and link information |
|
Publication Number: FHWA RD-03-081
Date: June 2003 |
||||||||||||||||||||||||||||||||||||||||||||
Updated Minimum Retroreflectivity LevelsFinal ReportPDF Version (837 KB)
PDF files can be viewed with the Acrobat® Reader® U.S. Department of Transportation Federal Highway Administration Research, Development, and Technology Office of Safety Research and Development Turner-Fairbank Highway Research Center 6300 Georgetown Pike McLean, Virginia 22101
ForewordReport FHWA-RD-03-081 presents the results of a study that updated the minimum levels of traffic sign retroreflectivity for regulatory, guide, and warning signs which had been generated in 1993. The research team identified the need to update the basic input parameters for headlight illumination patterns and intensity, the effects of larger vehicles in the and the associated changes in driver eye height and headlight positions, the new legibility requirements of the MUTCD, the needs of older drivers, and the performance features of new sign materials. A new analysis tool was developed that computed retroreflectivity needs considering the relative illumination provided by each headlight for traffic signs in various positions (right-side, left-side, and overhead) relative to the roadway. Detailed tables of minimum levels of traffic sign retroreflectivity were produced to allow analysis of the sensitivity of factors such as speed, driver accommodation levels, the features of available materials, sign legend, and other factors. The detailed tables were subsequently collapsed to address AASHTO concerns about the requirements being too complicated. The end result of these efforts was that the three tables from the 1993 research and the three tables from the recent research on overhead guide and street names signs were collapsed into a single table. This single table is described in this report. Sufficient copies of this report have been produced to allow distribution to FHWA division offices, resources centers and each state highway agency. Copies can be requested from the FHWA Office of Safety or the Office of Safety R&D. In addition, this report is available on-line through the FHWA electronic library at http://www.fhwa.dot.gov/research/tfhrc/programs/safety/index.cfm. Michael Trentacoste Notice This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for the contents or the use thereof. The report does not constitute a standard, specification, or regulation. The United States Government does not endorse products or manufacturers. Trade and manufacturers’ names appear in this report because they are considered essential to the object of the document. Technical Report Documentation Page
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized SI* (Modern Metric) Conversion Factors TABLE OF CONTENTS
LIST OF APPENDICESAppendix A: AASHTO Policy Resolution Appendix B: RAW Data From Mercier et.al. Appendix C: Subjective Results From National MR Workshops LIST OF FIGURESFigure 1. Minimum Luminance Data for Warning Signs Figures 2 a and b. Minimum Luminance Requirements Figure 3. Scatterplot of Data from Mercier et al. and TTI Figure 4. Comparison of Data for Older Drivers Only Figure 5. Effect of Contrast Ratio on Legibility Figure 6. Cumulative Percentage of Driver Population as a Function of Driver Age for Trips at Different Times of Day Figure 7. Rotational Sensitivity of four types of Retroreflective Sheeting Materials Figures 8 a and b. Observation Angle Profiles as a Function of Weathering Figures 9-45. Comparison of Human Subjects' Performance Against Demand Luminance Predicted by CARTS Using 15 Different Signs Figure 46. Results for the CURVE Sign (i.e., Bold Warning Sign) Figure 47. Results for the DIVIDED HIGHWAY ENDS Sign (i.e., Fine Warning Sign) Figure 48. Results for STOP Sign (i.e., White-on-Red Iconic Sign) LIST OF TABLESTable 1. Research Recommendations for Updated MR Levels Table 2. Threshold Luminance Values by Accommodation Level (cd/m2) Table 3. Replacement Luminance Values Table 4. Minimum Internal Contrast Criteria Table 5. Headlamp Descriptions Table 6. Vehicle Dimensions for MR Calculations Table 7. Initial MR Levels for Large Guide Signs Table 8. Initial MR Levels for Small Guide Signs Table 9. Assumed Characteristics and Criteria for Street Name Signs Table 10. Initial MR Levels for Street Name Signs Table 11. Inventory of Standard Size Warning Signs Table 12. Criteria for Text-Based Warning Signs Table 13. Initial Retroreflectivity Levels for Text Warning Signs Table 14. Initial Retroreflectivity Levels for Symbol Warning Signs Table 15. Criteria for SPEED LIMIT Signs Table 16. Initial Retroreflectivity Levels for SPEED LIMIT Signs Table 17. Criteria for KEEP RIGHT Signs Table 18. Criteria for ONE WAY Signs Table 19. Criteria for NO RIGHT TURN Signs Table 20. Initial MR Levels for KEEP RIGHT Signs Table 21. Initial MR Levels for ONE WAY Signs Table 22. Initial MR Levels for NO RIGHT TURN Signs Table 23. Criteria for STOP Signs Table 24. Initial MR Levels for STOP Signs Table 25. Criteria for DO NOT ENTER Signs Table 26. Initial Retroreflectivity Levels for DO NOT ENTER Signs Table 27. Updated MR Levels for Traffic Signs Table 28. Summary of Variability Across Sign Faces Table 29. Rotational Sensitivity of Unweathered Materials Table 30. Rotational Sensitivity of Weathered Materials Table 31. Description of NTPEP Panels Measured Table 32. Description of Signs Used in Visibility Study Table 33. Description of Signs Used in Nighttime Evaluations |