A review of the literature indicates that a luminance value of 3.2 cd/m2 should be the absolute minimum acceptable sign legend luminance value for proper legibility of overhead guide signs. Although a limited laboratory study, conducted as part of this investigation, suggests a minimum sign luminance of 13 cd/m2, the sample was small and the data varied considerably. Other researchers recommend higher values, including one who suggests 75 cd/m2 as an optimum. In view of these different opinions, we felt that a sign legend luminance (white letters) of 3.2 cd/m2 is a reasonably conservative value for signs located in areas with little or no ambient lighting and no oncoming traffic. Based on this minimum sign legend luminance of 3.2 cd/m2 and commonly used retroreflective signing materials, several cars evaluated in this study did not provide sufficient light toward overhead and left shoulder-mounted signs to produce minimal sign luminance unless type III material was used. One of the cars, using an HID lamp in a composite headlamp, did not provide sufficient sign illumination for the overhead and left shoulder-mounted signs, even if the signing material were of type III.


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    Titel :

    A field evaluation of retroreflective signs illuminated by headlights


    Beteiligte:
    Arens, J.B. (Autor:in)


    Erscheinungsdatum :

    1999


    Format / Umfang :

    16 Seiten, 4 Bilder, 5 Tabellen, 7 Quellen



    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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