Highway fog problems were analyzed and a fog visibility index was developed to quantify fog levels as a measure of detrimental effects on driver performance and traffic operations. The fog visibility index, which predicts the distance at which a vehicle stopped in fog can be seen, uses 'instrument' visibility and ambient light level as inputs. Although the fog index and the associated safe stopping speeds appear as unique functions of fog density and ambient background brightness, the actual sighting distance is a probability function. A survey of fog measuring instruments showed that scatter types appear to be the most suitable for general highway use, although all are subject to errors in patchy fog banks with single-instrument installations. Some advanced guidance systems appear technically feasible and may be economically practical in combination with freeway surveillance and control systems.


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    Title :

    Highway Fog - Visibility Measures and Guidance Systems


    Contributors:
    W. H. Heiss (author)

    Publication date :

    1976


    Size :

    52 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English






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