The operational efficiency of many two-lane highways depends on the opportunity for faster drivers to pass slower drivers. Where faster drivers encounter a slower driver and are unable to pass, platoons form and the level of service of the two-lane highway deteriorates. Passing Sight Distance (PSD) is provided in the design of two-lane highways to provide opportunities for faster drivers to pass where gaps in opposing traffic permit. Passing and nopassing zones are marked in the centerline of two-lane highways to indicate where it is legal for drivers to make such passing maneuvers. PSD design for two-lane highways is based on criteria in the AASHTO Green Book that were derived from older data and have been unchanged for many years. Marking of passing and no-passing zones are based on PSD criteria presented in the Manual on Uniform Traffic Control Devices (MUTCD). The MUTCD criteria are based on the values in a 1940 AASHO guide and represent a subjective compromise between sight distances computed for flying passes and sight distances computed for delayed passes. The marking PSD criteria are substantially less than the PSD criteria used in design. The MUTCD also provides guidance on minimum passing zone length of 120 m (400 ft) by stating that, where successive no-passing zones come within 120 m (400 ft) of one another, the no-passing-zone marking should be continued between them. A number of alternative PSD models were reviewed in the research. The alternative models that appear to most appropriately represent the PSD needs of passing drivers are those developed by Glennon and Hassan et al. Both of these models recognize that, in the early stages of a passing maneuver, the passing driver can easily and safely abort the passing maneuver.
Passing Sight Distance Criteria
2008
95 pages
Report
Keine Angabe
Englisch
Highway Engineering , Transportation & Traffic Planning , Transportation , Road Transportation , Highway design , Passing , Sight distances , Visibility , Marking , Revisions , Recommendations , Accident data , Criteria , Mathematical models , Highway characteristics , Passing Sight Distance (PSD) , Passing maneuvers , Alternative passing sight distance models , Two-lane highways
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