Nighttime Legibility of Ground-Mounted Traffic Signs as a Function of Font, Color, and Retroreflective Sheeting Type

Details

• Creators:
  Chrysler, Susan T. ; Carlson, Paul J. ; Hawkins, H. Gene
• Corporate Creators:
  Texas Transportation Institute. Texas A&M University
• Corporate Contributors:
  Texas Department of Transportation. Research and Technology Implementation Office ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Color Human Factors Legibility Night Visibility Retroreflectivity Sign Sheeting Traffic Signs Visibility
• Publication/ Report Number:
  FHWA/TX-03/1796-2
• Resource Type:
  Tech Report
• Geographical Coverage:
  Texas;United States
• Edition:
  September 1999 – August 2002
• Corporate Publisher:
  Texas Transportation Institute. Texas A&M University
• Abstract:
  A closed course nighttime legibility study measured legibility distance for 6-inch letters using Highway Series D and two experimental fonts, Clearview Condensed Road and a D-Modified font. The Clearview font has a thinner stroke width than Series D and was used for white-on-green signs. The D-Modified font has a thicker stroke width than Series D and was used for black letters on white, yellow, and orange backgrounds. Three types of retroreflective sheeting were tested: ASTM Types III, VIII, and IX. Forty-eight signs were used; all sign blanks were 12-inch x 30 inch with a border. Twenty-four participants, aged 55 - 75, drove a passenger sedan around a closed course at 30 mph while attempting to read ground-mounted signs on the right shoulder. Results showed no difference between drivers aged 55 - 64 and those aged 65 - 75. Overall legibility distances ranged from 143 ft to 206 ft, producing legibility indexes in the range of 24 - 34 ft of legibility per inch of letter height. Color was found to be a significant factor in legibility with yellow and white producing the longest legibility distances followed by green and then orange. Across all colors, retroreflective sheeting type was a significant factor with specific differences among sheeting dependent on color. The font results were surprising in that Highway Series D was better than or equivalent to both alternatives tested and the version of Clearview tested performed slightly worse than the standard font.
• Format:
  PDF
• Funding:
  0-1796
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:9dd9952f91c82ab0a01df81964f73e6a7d11d04147717b80882332615578a789005b4948073784b688319ee863764401cba4362486fba94f846a9e0d3bd2c9a3
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/86182/dot_86182_DS1.pdf
• File Type:
  [PDF - 894.71 KB ]