Experimental Analysis of Factors Affecting Nighttime Visibility of Traffic Signs

According to U.S. statistics, more than half of highway fatalities occurred at night. One contributing factor is nighttime visibility, which is considered one of the crucial elements in traffic safety. Retroreflective signs can potentially improve highway safety and prevent nighttime accidents by making traffic signs appear brighter and easier to be detected by road users. This study attempted to investigate underlying factors, including types of vehicles, coefficient of retroreflectivity, driving speed, height of traffic signs, and characteristics of road users, that could affect traffic sign visibility during nighttime. The authors applied systematic experimental design to examine these effects on legibility distance. A total of 27 subjects in three age groups were recruited for the field experiment during the nighttime on a rural road section in Thailand. Age of participants was controlled as a blocking factor in the experiment, while three traffic sign types and two vehicle types were separately examined. Statistical findings indicated that different types of traffic sign yielded different legibility distances. In addition, detection and legibility distances for passenger car were found to be significantly higher than the motorcycles’ counterpart by 7.5% and 18.2%, respectively. From the analysis of variance, the most significant factor affecting nighttime visibility of traffic signs was the traffic sign retroreflectivity. Findings would help developing a more appropriate guideline for installation of traffic signs so that such road furniture can guarantee the maximum safety of road users.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AND40 Visibility.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Choocharukul, Kasem
  • Chanhom, Patcharayut
• Conference:
  • Transportation Research Board 94th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2015-1-11 to 2015-1-15
• Date: 2015

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Maps; Photos; References; Tables;
• Pagination: 16p
• Monograph Title: TRB 94th Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Age groups; Automobiles; Fatalities; Legibility; Motorcycles; Night vision; Nighttime crashes; Retroreflectivity; Speed; Traffic control devices
• Geographic Terms: Thailand
• Subject Areas: Highways; Safety and Human Factors; I83: Accidents and the Human Factor; I85: Safety Devices used in Transport Infrastructure;

Filing Info

• Accession Number: 01550122
• Record Type: Publication
• Report/Paper Numbers: 15-0067
• Files: TRIS, TRB, ATRI
• Created Date: Jan 16 2015 8:29AM