A Procedure for Auditing Highway Alignments for the Effects of Sun Glare

The authors propose a geometric method to evaluate three dimensional highway alignments, either existing or proposed, for possible deleterious effects due to sun glare. Depending on the time of day and the position of the sun, serious traffic congestion and safety degradation can occur as a result of the blinding effect of the sun. The horizontal and vertical geometry of the roadway contribute directly to placing the viewing angle of the driver in a situation to be susceptible to these effects. The trajectory of the sun through the sky changes over the course of the year as a result of the axial tilt of the Earth, so these problems can occur at different times and at different locations during the year. The problem is most prevalent when the sun is low in the sky, either setting or rising, as roadway grades tend to be quite slight from a geometric perspective. In such conditions, however, the atmosphere plays a significant role in refracting the sunlight, causing the sun’s apparent position to be different than its actual position. The authors develop a mathematical method to determine, for a given geometrical description of a highway alignment, what locations, and at what times, that alignment might be susceptible to these problems. This information can then be used to develop alternative alignments that would not suffer so much from this potential safety hazard. The authors' calculations include astronomical algorithms to determine the vector direction of the sun from a given location on the highway, at any time during the year, as well as the optical refinements necessary to account for atmospheric refraction. Essentially, the output of the model is a list of locations and times that are expected to suffer from sun glare effects. Such an algorithm could serve as one of a number of road safety audits conducted in a safety review for a given alignment, or it could serve as an input to an automated highway design process whose objective function accounted for safety deficiencies of candidate alignments. The algorithm is motivated and developed in detail, and is tested against highway alignment data.

• Corporate Authors:

  Polytechnic University of Valencia

  Department of Transportation, Camino de Vera
  Valencia,   Spain  46022
• Authors:
  • Churchill, Andrew M
  • Lovell, David J
• Conference:
  • 4th International Symposium on Highway Geometric Design
  • Location: Valencia , Spain
  • Date: 2010-6-2 to 2010-6-5
• Publication Date: 2010

Language

• English

Media Info

• Media Type: CD-ROM
• Features: Figures; References;
• Pagination: 16p
• Monograph Title: 4th International Symposium on Highway Geometric Design, June 2-5, 2010, Valencia, Spain

Subject/Index Terms

• TRT Terms: Algorithms; Alignment; Geometric design; Glare; Highway design; Highway safety; Mathematical methods; Safety audits; Sun
• Subject Areas: Design; Highways; Safety and Human Factors; I20: Design and Planning of Transport Infrastructure;

Filing Info

• Accession Number: 01338132
• Record Type: Publication
• Files: TRIS
• Created Date: Apr 28 2011 1:01PM