A study is reported which investigated the effect of snow on the visibility of tail lights (especially with respect to designs which were clearly good or bad in their ability to minimize the effect of snow), and the relative merit of different tail light geometry as it effects the ability of following drivers to detect changes in relative speed of the lead vehicle. Recent trends in rear light design are reviewed. Observations were made of cars parked in a University parking lot just after a snow storm. The analysis of photographs reveals important design features which relate to obscuration by snow. The obscuration of taillights on moving cars is discussed and a recommendation is presented that consideration be given to multiple levels of illumination in the ratio 1:10:100 to be used at night, in the daytime and in fog respectively. It was observed that attenuation of light intensity is severe for dry packed snow, and that daytime visibility of running signal lights is severly affected by the presence of a thin covering of snow on the lenses. The results are presented of a test on the contrast needed to detect a red light glowing behind a shallow screen of snow under daylight conditions. Characteristics which lead to obscuration while underway are listed, and characteristics considered to aid in rear lights under snow condition are summarized. Vulnerability to damage was also investigated. The study of the effect of geometry on the ability of a following driver to detect changes in relative speed of the lead vehicle, involved a 1:18 scale simulator in which a model could be towed up and down a dark tunnel. Details are given of the investigation in which tail light configurations could be changed by mounting different masks over the rear compartment of the model. An attempt was also made to determine if binocular sight played a large role in the depth-perception task. The evidence indicates that vertically oriented lights on each side of the car enhance the ability of following to detect changes in relative speed. Recommendations, based on the study, are suggested.

  • Corporate Authors:

    Maine Department of Transportation

    Materials and Research Division, Box 1208, Hogan Road
    Bangor, ME  United States  04402
  • Authors:
    • Gibson, R C
  • Publication Date: 1975-6

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 39 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00098472
  • Record Type: Publication
  • Report/Paper Numbers: 75-3 Final Rpt.
  • Created Date: Sep 30 1975 12:00AM