Effect of Retroreflecting Performance for Traffic Signs by Driving Visibility Evaluation Under Foggy Conditions

For safe driving in foggy conditions it is important that drivers recognize warning signs and other traffic control devices. We report on the visibility and legibility of warning signs whose surfaces incorporate different retroreflective materials, as determined by subjects driving under clear and dense-fog conditions. The tests were conducted on a road in service under four visibility conditions: daytime clear, daytime dense fog, nighttime clear, and nighttime dense fog. A vehicle dynamics recorder was mounted on a test car that traveled both directions on a 4.5-km test section in Eastern Hokkaido, Japan. The authors installed curve warning signs with surfaces incorporating one of two retro-reflective materials. Five male drivers drove a test car under free-flow condition. The driver cued an experimenter in the back seat upon recognizing the warning sign (visibility recognition) and again upon determining its meaning (legibility recognition). The experimenter in the rear seat recorded the time of each cue. The distance at which the warning sign was recognized (visibility distance) and that at which the sign meaning was determined (legibility distance) were calculated from driving speed and time taken to travel from the points of visibility and legibility to the sign. Visibility and legibility distances in daytime dense fog and nighttime dense fog tended to be greater for the signs incorporating wide-angle prism retro-reflective material than for signs incorporating encapsulated-lens retro-reflective material. The findings demonstrate that installing traffic signs with high retroreflectivity can contribute to driving safety by improving visibility and legibility under fog.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Photos; References; Tables;
  • Pagination: 16p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01046379
  • Record Type: Publication
  • Report/Paper Numbers: 07-1387
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 5:59PM