The visibility level necessary for the performance of a visual task is defined relative to the visibility reference function. This function, as at present proposed for use by The Commission International D'eclairage is to be considered illustrative only at background luminances below 1 cd/sq M. It may therefore not be representative of actual threshold values for visual tasks performed in this luminance region. Driving at night on unlighted roads with dipped beam is an example of such a task. It is shown that experimental data for this case indicate lower threshold values than those given by the visibility reference function. (A) /TRRL/

  • Availability:
  • Corporate Authors:

    Illuminating Engineering Society

    York House, 199 Westminster Bridge Road
    London SE1 7UN,   England 
  • Authors:
    • Hisdal, B
  • Publication Date: 1977

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00170301
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Jun 28 1978 12:00AM