DETERMINATION OF SIGN LETTER SIZE REQUIREMENTS FOR NIGHT LEGIBILITY BY COMPUTER SIMULATION

A PREVIOUSLY DEVELOPED COMPUTER SIMULATION PROGRAM WAS USED TO EXAMINE THE ADEQUACY OF LETTER SIZES ON EXISTING SIGNING ALONG A 20-MILE STRETCH OF INTERSTATE HIGHWAY. A TOTAL OF 63 SIGNS WERE ANALYZED IN DETAIL FOR MINIMUM REQUIRED LEGIBILITY UNDER THREE SETS OF CONDITIONS: DAYLIGHT, HIGH-BEAM ILLUMINATION, AND LOW-BEAM ILLUMINATION. ALTHOUGH THE STANDARDS OF SIGNING, ACCORDING TO ACCEPTED TRAFFIC ENGINEERING CRITERIA AND ACCORDING TO ADHERENCE TO PERTINENT SIGNING MANUALS, WERE FOUND TO BE ABOVE AVERAGE, COMPUTER ANALYSIS REVEALED CONSIDERABLE DEFICIENCIES. THESE DEFICIENCIES WERE MOST PRONOUNCED FOR LOW-BEAM ILLUMINATION AND WERE ESPECIALLY SEVERE FOR OVERHEAD SIGNS. THE ANALYSIS REVEALED LETTER SIZE DEFICIENCIES FOR 27 PERCENT OF ALL SIGNS FOR DAYLIGHT, 35 PERCENT FOR HIGH-BEAM ILLUMINATION, AND 49 PERCENT FOR LOW-BEAM ILLUMINATION. FOR GUIDE SIGNS, THE CORRESPONDING FIGURES WERE 39, 44, AND 63 PERCENT. ONLY 1 OF 13 OVERHEAD SIGNS WAS FOUND TO BE ADEQUATE FOR LOW-BEAM ILLUMINATION. CONSIDERABLE VARIATION IN REQUIRED LETTER HEIGHT WAS FOUND EVEN BETWEEN IDENTICAL SIGNS. ANALYSIS OF THESE VARIATIONS AND OF THE OTHER DEFICIENCIES REVEALED A DISPROPORTIONATE INFLUENCE OF APPARENTLY MINOR CHANGES IN APPROACH HORIZONTAL AND VERTICAL ALIGNMENT. /AUTHOR/

• Record URL:
  • http://onlinepubs.trb.org/Onlinepubs/hrr/1971/366/366-005.pdf
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309019818
• Supplemental Notes:
  • Sponsored by Committee on Traffic Control Devices and presented at the 50th Annual Meeting. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • King, Gerhart F
• Publication Date: 1971

Media Info

• Media Type: Print
• Features: Appendices; Figures; References; Tables;
• Pagination: pp 48-63
• Monograph Title: Traffic control and driver information
• Serial:
  • Highway Research Record
  • Issue Number: 366
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Alignment; Brightness; Computer programs; Design; Height; Legibility; Lettering; Night; Night visibility; Simulation; Traffic signs; Visibility
• Old TRIS Terms: Letters
• Subject Areas: Design; Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00226188
• Record Type: Publication
• ISBN: 0309019818
• Report/Paper Numbers: HS-011 999
• Files: TRIS, TRB
• Created Date: Mar 20 1972 12:00AM