NCHRP Report 524: Safety of U-Turns at Unsignalized Median Openings

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Table of Contents
Front Matter R1-R8
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

Table of Contents

Front Matter R1-R8

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