SIGN BRIGHTNESS IN RELATION TO LEGIBILITY

USING AN INTERNALLY ILLUMINATED SIGN, VARIOUS COMBINATIONS OF BLACK-AND-WHITE LETTERS AND BACKGROUNDS WERE TESTED IN THE FIELD AT NIGHT UNDER A WIDE RANGE OF AMBIENT LIGHTING CONDITIONS TO DETERMINE THE RELATIONSHIP BETWEEN SIGN LUMINANCE AND LEGIBILITY. THREE AGE GROUPS FOR THE OBSERVERS WERE USED. CONTRAST LEVEL AND DIRECTION WERE CONTROLLED AS WELL AS THE LEVEL OF HEADLAMP GLARE. MINIMUM AND MAXIMUM BRIGHTNESS VALUES ARE DISCUSSED FOR TYPICAL RURAL, SUBURBAN, AND DOWNTOWN URBAN AMBIENT ILLUMINATION CONDITIONS. IF ALL SIGNS WERE ILLUMINATED UNIFORMLY AT 20 FT-L, LEGIBILITY WOULD BE VERY GOOD, EVEN IF LUMINANCES AS LOW AS 10 FT-L WERE ALLOWED AT THE DARKEST PART OF THE SIGN. /BPR/

• Supplemental Notes:
  • Hpr, 62 G-118, HPR-1/3/
• Corporate Authors:

  Michigan Department of State Highways

  State Highways Building, PO Drawer K
  Lansing, MI  United States  48904
• Authors:
  • Allen, T M
  • Smith, G M
  • Janson, M H
  • Dyer, F N
• Publication Date: 1966-5

Subject/Index Terms

• TRT Terms: Brightness; Environment; Field tests; Illuminated traffic signs; Legibility; Lettering; Night; Traffic signs
• Uncontrolled Terms: Observation
• Old TRIS Terms: Letters
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00224822
• Record Type: Publication
• Source Agency: Bureau of Public Roads /US
• Files: TRIS, STATEDOT
• Created Date: Aug 1 1994 12:00AM