Citation

Harwood DW, Glennon JC. Transp. Res. Rec. 1976; 601: 45-50.

Copyright

(Copyright © 1976, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Current design and marking standards for passing and no- passing zones are based on the results of field studies conducted more than 35 years ago. Many of the assumptions used to derive these standards are not valid for current highway operations. In addition, design and marking standards are almost exclusively concerned with passing sight distance. Design standards contain no provision to establish the minimum length over which the design passing sight distance must be made available to the passing driver to constitute a safe passing zone. Marking standards indirectly set the minimum length of passing zones at 122 m (400 ft). This zone length is inadequate for the majority of higher speed passes. A review of recent research, especially studies dealing directly and design or marking practice, indicates that sufficient data are available to develop design and marking standards based on the contemparary field measurements. The results of a study on short passing zones demonstrate the safety and operational deficiences of passing zones less than 268 m (880 ft) long. Therefore, it is recommended that design and marking standards consider both passing sight distance and passing zone length. Because the design of highway geometrics should be based on analysis of subsequent highway operations, the authors recommend that design and marking standards be identical. Specific criteria for the design and marking of passing and no-passing zones are suggested.