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Title: DEVELOPMENT OF VISIBILITY ASSESSMENT METHODS WITH DIGITAL IMAGES UNDER FOGGY CONDITIONS
Accession Number: 00977229
Record Type: Component
Record URL: Availability: Transportation Research Board Business Office 500 Fifth Street, NW Find a library where document is available Abstract: Basic methods are proposed for assessing poor visibility by using digital images from a road monitoring camera. An experiment was performed over 5 days in 2002 under artificial fog at a laboratory of the National Institute for Land and Infrastructure Management in Tsukuba, Japan. Twenty-one Landolt circles were prepared as targets, each with a different variation of Landolt circle (7 circle sizes x 3 circle-contrast levels). Digital image (8 bits, red-green-blue), illuminance, and transmissivity under artificial fog were recorded together while five subjects assessed the visibility of the circle. First, the digital contrast of the Landolt circle was examined in a digital image in terms of its applicability as a visibility assessment value. Second, the average intensity of grayscale (AIG) of the entire cutout image was examined in terms of its applicability as a visibility assessment value. The magnitude of AIG represented the difference in digital intensities within the image. Digital contrast and AIG were compared with the subjective visibility assessment values (SVAV) given by the subjects. During fog, both digital contrast and AIG increased as transmissivity increased. Relationships were found between both these values and SVAV. However, when digital contrast was used, the relationships depended on circle size. When AIG was used, the relationships depended on SVAV and not on circle size or circle-contrast level. These results suggest that AIG might be more appropriate than digital contrast for assessing subjective visibility level during fog.
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: HAGIWARA, TKizaka, KFujita, SPagination: p. 95-108
Publication Date: 2004
Serial: ISBN: 0309094542
Features: Figures
(9)
; Photos
(1)
; References
(8)
; Tables
(1)
TRT Terms: Uncontrolled Terms: 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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