The Effect of Diagrammatic Signing at Head Speed Interchanges: Final Report

Report No: 73-R53

Published in 1974

About the report:

Improvements in highway guide signing at interchange areas are needed to reduce driver confusion and the accidents that result from it. One possible means of improving traffic operations within interchange areas is through the use of diagrammatic signs that give a graphic representation of the highway or interchange ahead. This study consisted of a laboratory investigation of the effect of diagrammatic signs at three interstate interchanges, and a field study of one of these. The results of the study revealed several considerations which should be of benefit in the design and evaluation of diagrammatic signing. First, through the use of a laboratory procedure utilizing motion picture segments to simulate actual roadway conditions, diagrammatic signs, rather than the existing conventional signs, were recommended for the three sites studied. The field study, however, indicated that the new diagrammatic sign observed in the field did not significantly reduce the number of erratic maneuvers. Although there were certain limitations placed on this study resulting from an abbreviated field phase, the study does propagate an awareness of the many variables which could influence results found from either laboratory or field studies.

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: February 6, 2024

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