Determining Visibility Distance of Signs Installed on the Roadside Using Videologs
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Date
2003-05-16
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Abstract
The purpose of traffic signs is to provide information for the orderly movement that guides all road users as to direction, regulations and warnings. A driver may be able to view sign sheetings from a long distance with no sight obstruction. However, there are many cases in which the driver's line of sight is blocked by obstructions, such as trees, hills, curves, and other signs. These obstructions may reduce the effectiveness of the sheetings and therefore the frequency of safe response by drivers. The objectives of this project are to determine the distribution of the visibility distance for obstructed and unobstructed signs and to identify reasons for being obscure using videologs. The videologs contain images that can be used for this visibility distance study with the benefits of less cost, less potential danger, and less time than data obtained from a manual field survey. Most signs were obstructed. A little more than half of the obstructions were curves and hills, and trees were the most prevalent obstruction in the urban area that was biggest problem among the road types. About 25.4% of obstructed signs had less than 400 feet of visibility distance. In order to avoid the possible reduction of the effectiveness of traffic signs, sign placement should be considered during geometric highway design, and the impact of trees that may be growing should be taken into consideration.
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Keywords
Traffic signs, Visibility distance, Videologs
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Degree
MS
Discipline
Civil Engineering
