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Title: FOG LUMINANCE EVALUATION IN DAYTIME
Accession Number: 00977227
Record Type: Component
Record URL: Availability: Transportation Research Board Business Office 500 Fifth Street, NW Find a library where document is available Abstract: In daytime, fog creates a luminous veil that impairs the visual indices required by motorists to coordinate their task of driving. The level of fog luminance depends on many parameters. A method is described to compute the luminance of a fog layer on the basis of its optical depth, the droplet size distribution, and the relative position of both the sun and the motorist. The results are then analyzed and indicate that fog luminance depends to a great extent on the direction of observation with respect to the sun. Except when the motorist is traveling toward the sun, the fog luminance follows the variations of horizontal illuminance, which increases with the altitude of the sun yet decreases with droplet size distribution. In most instances, the influence of the optical depth calculated over the height of the fog layer remains small. Only when facing the sun in a fog with droplet diameters less than or equal to 1 micron does the luminance increase significantly as optical depth decreases. The impact on the visibility parameters is presented.
Supplemental Notes: This paper appears in Transportation Research Record No. 1862, Traffic Control Devices, Visibility, and Rail-Highway Grade Crossings 2004.
Monograph Accession #: 00977217
Language: English
Corporate Authors: Transportation Research Board 500 Fifth Street, NW Authors: Paulmier, GPagination: p. 82-88
Publication Date: 2004
Serial: ISBN: 0309094542
Features: Figures
(7)
; References
(8)
Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors; I73: Traffic Control
Files: TRIS, TRB, ATRI
Created Date: Aug 27 2004 12:00AM
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