CALCULATION OF VISIBILITY IN ROAD LIGHTING

In the present report a method for calculating visibility under road lighting conditions has been described. The method will cover most situations met in road lighting and takes into account the 3 most important parameters determining the visibility of objects on lit roads: different shape and size of the objects, non-uniform luminances on the objects as will be the case when three-dimensional objects are placed in a road lighting installation, and non-uniform luminances in the background and surroundings of the object. The method utilizes a summation of visibility levels of subelements of the objects by means of a distance weighting function, which introduces the effect of size and shape of the object. This distance weighting function can with great accuracy calculate the effect of the size of the object, but it has not been proved conclusively that it can describe the effect of different shapes, although there is a good indication of this for relatively simple shapes. The method should, however, not be used on objects with a very complicated shape, unless the calculations are checked by measurements. The effect of non-uniform luminances in the surroundings of the object is calculated by assuming that each element of the surrounding has an effect on the contract sensitivity of the same character as a glaring light source and that the effect of each element can be summed. An important new principles is that not only areas with luminances higher than that of the immediate surrounding of the object have an effect, but also areas with lower luminances, and that the effect of the latter can be calculated by the same formula as the effect of the former. The calculation is carried out by means of the conventional formula for disability glare, but constant and exponent in the formula have been given higher values for small angles. The principle of summation of the effect of all the elements has not been fully proved, but as a first approximation it seems to be adequate. /Author/

  • Corporate Authors:

    Danish Illuminating Engineering Laboratory

    ,   Denmark 
  • Authors:
    • Frederisksen, E
    • Rotne, N
  • Publication Date: 1978-3

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 90 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00184560
  • Record Type: Publication
  • Source Agency: National Safety Council Safety Research Info Serv
  • Report/Paper Numbers: Report No. 17
  • Files: TRIS
  • Created Date: Feb 3 1979 12:00AM