Traffic Flow Evaluation of Pavement Inset Lights for Use During Fog: Before Phase

Report No: 76-R6

Published in 1975

About the report:

 Reduced visibility resulting from fog presents a very hazardous condition on the highway because of the inability of motorists to readily observe pavement markings and signs, and other vehicles. Afton Mountain, which is traversed by Interstate 64, often is the site of such reduced visibility because of the low cloud covering the mountain top during periods of rain. An acute awareness of the fog problem on Afton Mountain led to a decision by the Virginia Department of Highways and Transportation to install, a lighting system consisting of pavement inset lights and low level illumination lights to aid motorists during periods of fog. In addition to the lighting system, a series of variable speed signs will be installed in an attempt to regulate vehicular speeds.

It was, therefore, the purpose of this research to investigate the traffic flow characteristics during fog within the system of pavement inset lights installed on Interstate 64 across Afton Mountain. This phase of the project was limited to the collection of before data for the inset lights installed on the main line only. It was felt that the amount and reliability of before data should be assured before embarking on an after data collection phase. The time period available for collection of before data was limited since the inset lights will be placed in regular operation as soon as possible, making it difficult to accurately predict the amount of data which would be available for analysis as a result of the variability in the frequency of fog adequate for the purpose of the study. It is the intent of this report to summarize the data accumulated to date and evaluate their reliability. Detailed analyses of each parameter observed will not be made, though various comments concerning the data will he included.

Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.


  • Frank D. Shepard

Last updated: January 29, 2024

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