This study is concerned with the legibility of symbolic signs proposed for use in Dallas, Texas. Thirty-four experimental subjects viewed the signs and an acuity chart, binocularly with corrected vision. Findings of the study were as follows: Legibility distances of different elements of the signs differed markedly. On the average, symbols were identified at over 5 times the distance of word messages. Messages with large lettering were identified at about twice the distance of messages with small lettering on the same sign. These disparities in legibility may be reduced by shortening messages, employing capital letters, and using larger, more uniform size print, as prescribed in the Manual on Uniform Traffic Control Devices. Symbol threshold visual angle averaged 10.5 minutes, compared to 4.19 minutes for letter lines, and 3.3 minutes for the Snellen E Chart. At maximum seeing distance, symbols would have to be more than twice the size to be identied. These results suggest that symbol legibility can be considerably increased by improving the symbol design. The conventional "parking prohibited" symbol is difficult to read. An experimental symbol with a large slash which extended beyond the circle gave double the legibility distance of the conventional symbol. The legibilities of the four symbols intercorrelated highly, but showed low correlation with visual acuity and word message legibilities. The findings suggest that abilities other than visual acuity are involved in identifying parking symbols. Predicted legibility distances are given in table 3 for signs ranging from 1 to 4 ft (0.3 to 1.2m) in size. These projections are given for the average driver and for the 94th percentile (poorly sighted) driver. /Author/

  • Availability:
  • Corporate Authors:

    Federal Highway Administration

    Office of Research and Development, 1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Gordon, D A
    • Boyle, J A
  • Publication Date: 1977-9

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00167582
  • Record Type: Publication
  • Files: TRIS, USDOT
  • Created Date: Feb 16 1978 12:00AM