NCHRP Report 524: Safety of U-Turns at Unsignalized Median Openings
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NCHRP Report 524:
Safety of U-Turns at Unsignalized Median Openings
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TRB's National Cooperative Highway Research Program (NCHRP) Report 524: Safety of U-Turns at Unsignalized Median Openings includes recommended guidelines for locating and designing unsignalized median openings, and a methodology for comparing the relative safety performance of different designs.


Publication Info

142 pages | 8.5 x 11

Table of Contents

skim chapter
Front Matter i-viii
Summary 1-2
Organization of This Report 3-4
Location of Median Openings 5-5
Spacing of Median Openings 6-6
Safety of Median Openings 7-7
Median Width 8-9
Safety Effects of Median Treatments (Raised/Depressed/Flush/TWLTL) 10-14
Safety Effects of Increasing U-Turn Maneuvers Through Use of Nontraversable Medians 15-15
Left-Turn Lanes 16-17
Median Acceleration Lanes 18-19
Sight Distance at Median Openings 20-20
Indirect Left-Turn Maneuvers 21-23
Access Management 24-24
Spacing Between Access Points 25-25
Effects of Adjacent Traffic Signals 26-26
Location and Design of Median Openings 27-27
Treatment of U-Turns at Median Openings 28-30
Median and Roadway Widths to Accommodate U-Turn Maneuvers 31-31
Mitigation Measures for Safety Problems 32-32
Factors Used in Classification of Median Opening Designs 33-33
Overview of Typical Median Opening Designs 34-41
Factors That Influence the Safety and Operational Performance of Median Openings 42-51
Relative Safety of Median Opening Designs Based on Traffic Conflict Points 52-52
Combinations of Median Openings Along Arterial Streets 53-58
Catalog of Existing Median Openings 59-61
Data Collection and Analysis for Selected Median Openings 62-67
Median Opening Accident Frequencies 68-68
Median Opening Accident Rates 69-70
Median Opening Conflict Rates 71-71
Comparison of Median Opening Accident and Conflict Rates 72-73
Combinations of Median Openings 74-78
Conclusions 79-79
Recommendations, 80-80
References 81-82
Appendix A - Highway Agency Survey Questionnaire 83-89
Appendix B - Summary of Survey Responses From State and Local Highway Agencies 90-105
Appendix C - Guidelines for the Use, Location, and Design of Unsignalized Median Openings 106-133
Abbreviations used without definitions in TRB publications 134-134

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