OPTIMAL AND REPLACEMENT LUMINANCES OF TRAFFIC SIGNS: A REVIEW OF APPLIED LEGIBILITY RESEARCH

This study reviewed applied research on sign legibility to obtain information regarding optimal and replacement luminance values of retroreflective traffic signs. The report presents tabular summaries of 18 experimental studies, followed by a synthesis of findings in terms of luminance recommendations and corresponding retroreflectance values. The reviewed data suggest that the signs having light (white, yellow, or orange) backgrounds with black legends placed in low luminance surrounds, the optimal luminance of the background is 75 cd/Sq m. For fully reflectorized signs the optimal luminance of one component (legend or background) depends on the given luminance of the other component. The data suggest that for these signs the optimal legend-to-background contrast is 12:1. Assuming legibility criteria of 6 m/cm of letter height for younger drivers and 4.8 m/cm for older drivers the data suggest that the replacement luminance is 2.4 cd/sq m. This applies to light legends with dark backgrounds (green, blue, red, or brown) having luminance of up to 0.4 cd/sq m, and to light backgrounds (white, yellow, or orange) with black legends. Using these optimal and replacement luminance values, optimal and replacement retroreflectance values were derived for signs placed in four locations, illuminated by U.S. or European low-beam headlighting systems. The values for generally ideal conditions are presented in Tables 1 and 2. Additionally, Table 3 lists possible correction factors for some less than ideal conditions.

• Corporate Authors:

  University of Michigan Transportation Research Institute

  2901 Baxter Road
  Ann Arbor, MI  United States  48109-2150

  Three M Company

  3M Center
  St Paul, MN  United States  55144
• Authors:
  • Sivak, M
  • Olson, P L
• Publication Date: 1983-12

Media Info

• Features: References; Tables;
• Pagination: 37 p.

Subject/Index Terms

• TRT Terms: Age; Design; Drivers; Equipment replacement; Low beamed headlamps; Luminescence; Luminous materials; Retroreflection; Signs; Symbols; Traffic signs
• Uncontrolled Terms: Background (Traffic signs); Driver age; Replacement; Sign legend
• Old TRIS Terms: Low beamed headlights; Luminous sign; Retrodirective reflection; Traffic sign design
• Subject Areas: Design; Highways; Maintenance and Preservation; Operations and Traffic Management; I73: Traffic Control;

Filing Info

• Accession Number: 00396523
• Record Type: Publication
• Source Agency: National Highway Traffic Safety Administration
• Report/Paper Numbers: UMTRI-83-43 Final Rpt., HS-037 576
• Files: HSL, TRIS, ATRI, USDOT
• Created Date: Aug 31 1985 12:00AM