Relative visibility of increased legend size vs brighter materials for traffic signs

Static and dynamic legibility studies were conducted to investigate the effects of level of reflectivity, letter series, stroke width, letter spacing, font, letter height, and driver age. The dynamic study also considered the effect of sign size and retroreflectivity on the level of conspicuity. As expected, driver age had the largest effect on both legibility and conspicuity. In fact, the daytime legibility for older drivers is almost as poor as night legibility. Level of retroreflectivity, letter series, and letter height all had a significant effect on legibility. Increases in letter height resulted in proportionate increases in legibility up to about 600 ft (183 m). In most cases, stroke width, letter spacing, and font were not significant; however, with fully retroreflective signs, a narrow stroke width significantly increased the legibility of high-contrast signs. Using spacing narrower than the standard spacing did significantly reduce legibility. With regard to conspicuity, 36-in (0.91 m) signs with type I sheeting were found to have detection distances equivalent to 24-in (0.61 m) signs with type VII sheeting. Black-on-white signs were found to have much shorter detection distances than black-on-orange or white-on-green signs. Cost comparisons (excluding life-cycle costs) using the date available suggested that larger signs with type I sheeting were less expensive than smaller signs with type VII material which provided similar performance. The effects of other materials with brightness between type I and type VII were not of significant magnitude to provide reliable cost evaluations.

• Corporate Authors:

  United States. Federal Highway Administration (FHWA). Office of Safety and Traffic Operations R&D

  McLean, Virginia  United States 
• Authors:
  • Mace, D J
  • Garvey, P M
  • Heckard, R F
• Publication Date: 1994-12

Language

• English

Media Info

• Pagination: 44p
• Serial:
  • Issue Number: FHWA/RD-94-035

Subject/Index Terms

• TRT Terms: Age; Color; Legibility; Lettering; Reflectivity; Retroreflectivity; Size; Traffic signs; Visibility distance
• ATRI Terms: Age; Colour; Conspicuity; Dimension; Legibility; Lettering; Reflectivity; Retroreflectivity; Traffic sign; Visibility distance
• Subject Areas: Safety and Human Factors;

Filing Info

• Accession Number: 01400989
• Record Type: Publication
• Source Agency: ARRB
• Files: ITRD, ATRI, USDOT
• Created Date: Aug 23 2012 7:54PM