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Publication Number:  FHWA-HRT-16-064    Date:  November 2016
Publication Number: FHWA-HRT-16-064
Date: November 2016

 

Traffic Bottlenecks: Identification and Solutions

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FOREWORD

The far-reaching detrimental impacts on mobility, the environment, and the economy caused by recurring congestion are well known. This report adds to the vast amount of research on congestion mitigation by developing a new approach for ranking traffic bottlenecks, introducing a new playbook of 70 bottleneck mitigation strategies, conducting a benefit-cost analysis of 5 low-cost bottleneck mitigation strategies, and introducing 3 new bottleneck mitigation strategies. This report describes a data-driven congestion and bottleneck identification software tool and details low-cost operations-focused solutions, including dynamic lane use, contraflow or reversible lane use, hard shoulder lane use, lane width reduction, and modest extension of auxiliary lanes. This report will be of interest to practitioners involved in the transportation operations discipline.

Brian Cronin
Director, Office of Operations
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

 

Technical Report Documentation Page

1. Report No.
.
FHWA-HRT-16-064
2. Government Accession No. 3. Recipient’s Catalog No.
4. Title and Subtitle

Traffic Bottlenecks: Identification and Solutions
5. Report Date

November 2016
6. Performing Organization Code
7. Author(s)

David Hale, Ramanujan Jagannathan, Michalis Xyntarakis, Peng Su, Ximiao Jiang, Jiaqi Ma, Jia Hu, and Cory Krause
8. Performing Organization Report No.
9. Performing Organization Name and Address

Leidos, Inc.
11251 Roger Bacon Drive
Reston, VA 20190
10. Work Unit No. (TRAIS)
11. Contract or Grant No.

DTFH61-12-D-00020
12. Sponsoring Agency Name and Address

Office of Operations Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296
13. Type of Report and Period Covered

Research Report
14. Sponsoring Agency Code

HRDO-20
15. Supplementary Notes

The Contracting Officer’s Representative was Joe Bared, HRDO-20.
16. Abstract

The objective of this project was to develop practical methods for prioritizing and mitigating traffic bottlenecks, which are one of the top causes of surface transportation congestion in the United States. Through this project, the following were developed: a new approach for ranking traffic bottlenecks, a new playbook of 70 bottleneck mitigation strategies, a benefit-cost (B/C) analysis of 5 low-cost bottleneck mitigation strategies, and 3 new bottleneck mitigation strategies.

Regarding the new approach for ranking traffic bottlenecks, a data-driven congestion and bottleneck identification software tool was created with numerous performance measures. In parallel, extensive traffic simulations were conducted to assess the operational benefits of underrated strategies as opposed to popular strategies, like ramp metering, which have been extensively researched and implemented in recent decades. Moreover, the project focused on low-cost solutions as opposed to solutions requiring excessive infrastructure investments or advanced vehicle technologies. These solutions involved dynamic lane use, contraflow or reversible lane use, hard shoulder lane use, lane width reduction, and modest extension of auxiliary lanes. Research results demonstrated that these solutions produced favorable B/C ratios with only minor modifications to existing infrastructure. The project further developed preliminary design guidance on signing, signalization, and striping for these strategies, with a follow-on human factors study for two of the strategies.
17. Key Words

Research, Traffic bottlenecks, Dynamic lane use, Traffic simulation
18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
http://www.ntis.gov
19. Security Classif. (of this report)

Unclassified
20. Security Classif. (of this page)

Unclassified
21. No. of Pages

179
22. Price
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

SI* (Modern Metric) Conversion Factors

TABLE OF CONTENTS

EXECUTIVE SUMMARY

CHAPTER 1. INTRODUCTION

CHAPTER 2. BOTTLENECK IDENTIFICATION

CHAPTER 3. BOTTLENECK MITIGATION CONCEPTS

CHAPTER 4. COST-EFFECTIVE SOLUTIONS FOR BOTTLENECK MITIGATION

CHAPTER 5. INNOVATIVE SOLUTIONS FOR BOTTLENECK MITIGATION

CHAPTER 6. CONCLUSIONS

APPENDIX. PLAYBOOK OF BOTTLENECK SOLUTIONS

REFERENCES

LIST OF FIGURES

Figure 1. Graph. Traffic congestion causes from 2004
Figure 2. Graph. Vehicle delay versus degree of traffic congestion
Figure 3. Screenshot. CBI software tool
Figure 4. Screenshot. Conventional lanes at a signalized diamond interchange
Figure 5. Screenshot. DRLT lanes at a signalized diamond interchange
Figure 6. Graph. Survey results for defining congestion
Figure 7. Flowchart. Generation of STMs via measurements or models
Figure 8. Graph. Reliability analysis box
Figure 9. Graph. Concept of bottleneck intensity (percentage of analysis box that is congested)
Figure 10. Screenshot. Congestion identification heat map from the RITIS Web site
Figure 11. Screenshot. Bottleneck rankings from the RITIS Web site
Figure 12. Equation. Impact factors for bottleneck rankings
Figure 13. Graph. STM used to compute bottleneck intensity
Figure 14. Graph. ARM based on bottleneck intensity
Figure 15. Graph. ARM illustrating relatively good bottleneck reliability
Figure 16. Graph. ARM illustrating relatively poor bottleneck reliability
Figure 17. Screenshot. CBI tool with ARM (upper right) and speed drop (lower right)
Figure 18. Equation. Delay per vehicle on each traffic message channel (TMC)
Figure 19. Equation. Vehicle-hours of delay on each TMC
Figure 20. Screenshot. Newer CBI software tool featuring vehicle-hours of delay
Figure 21. Graph. ARM illustrating relatively good bottleneck reliability based on vehicle-hours of delay
Figure 22. Graph. ARM illustrating relatively poor bottleneck reliability based on vehicle-hours of delay
Figure 23. Graph. Comparison of bottleneck locations based on BII—I-695 example
Figure 24. Graph. Comparison of bottleneck locations based on BII—I-495 example
Figure 25. Graph. Comparison of bottleneck locations based on BII—I-895 example
Figure 26. Graph. STM before wavelet filtering
Figure 27. Graph. STM after wavelet filtering
Figure 28. Screenshot. Example of missing data in the CBI tool
Figure 29. Flowchart. Framework to identify causes of bottlenecks
Figure 30. Illustration. Example of LT congestion prior to DLG
Figure 31. Illustration. Example of LT congestion after DLG
Figure 32. Equation. Minimum acceptable demand volumes for DLG
Figure 33. Equation. Minimum change in turn volumes for DLG
Figure 34. Equation. Minimum change in TH volumes for DLG
Figure 35. Equation. Different congestion in adjacent movements for DLG
Figure 36. Equation. Sufficient turn movement congestion for DLG
Figure 37. Equation. Minimal TH movement congestion for DLG
Figure 38. Equation. Severe turn movement congestion for DLG
Figure 39. Illustration. Morning peak configuration for case study 1
Figure 40. Illustration. Afternoon peak configuration for case study 1
Figure 41. Illustration. Lane assignment before DLG for case study 1
Figure 42. Illustration. Lane assignment after DLG for case study 1
Figure 43. Illustration. Traffic demand for case study 2
Figure 44. Equation. Monetary savings for each vehicle-hour of delay reduction
Figure 45. Equation. Total hourly time savings for the DLG example
Figure 46. Equation. Annual cost savings for the DLG example
Figure 47. Photo. Upstream DLG signage in Maryland
Figure 48. Illustration. DMC
Figure 49. Illustration. Merging of multiple two-lane freeways (closure on route B)
Figure 50. Illustration. Merging of multiple two-lane freeways (closure on route A)
Figure 51. Illustration. Merging of three- and two-lane freeways (closure on route B)
Figure 52. Illustration. Merging of three- and two-lane freeways (closure on route A)
Figure 53. Illustration. Merging of one-lane ramp and two-lane mainline (closure on mainline)
Figure 54. Illustration. Merging of one-lane ramp and three-lane mainline (closure on mainline)
Figure 55. Illustration. Merging of one-lane ramp and four-lane mainline (closure on mainline)
Figure 56. Equation. Simulated values and mean values over all simulation replications
Figure 57. Equation. RRMSE
Figure 58. Equation. FHWA GEH criteria
Figure 59. Equation. Total hourly time savings for the DMC example
Figure 60. Equation. Total daily time savings for the DMC example
Figure 61. Equation. Annual cost savings for the DMC example
Figure 62. Illustration. Automated gate option for DMC
Figure 63. Photo. Real-world image of an automated gate
Figure 64. Illustration. Acceleration lane length schematic (three-lane configuration)
Figure 65. Illustration. Acceleration lane geometry
Figure 66. Graph. Total delay for three mainline lanes and 40-mi/h ramp speed
Figure 67. Graph. Total delay for three mainline lanes and 30-mi/h ramp speed
Figure 68. Graph. Total delay for four mainline lanes and 40-mi/h ramp speed
Figure 69. Graph. Total delay for four mainline lanes and 30-mi/h ramp speed
Figure 70. Equation. Total daily time savings for extended acceleration lanes
Figure 71. Equation. Annual cost savings for extended acceleration lanes
Figure 72. Illustration. HSR strategy schematic
Figure 73. Illustration. Base year analysis of reducing lane widths to add new lanes
Figure 74. Illustration. Equivalent freeway scenario with five mainline lanes
Figure 75. Graph. Speed reduction as a function of lane width
Figure 76. Illustration. Dynamic HSR for incident response
Figure 77. Equation. Free-flow speed from lane width and lateral clearance
Figure 78. Illustration. Typical signalized diamond interchange with back-to-back LT lanes
Figure 79. Map. Selected signalized diamond interchange case study
Figure 80. Illustration. Interchange traffic patterns
Figure 81. Screenshot. Georgetown Pike interchange with conventional lanes
Figure 82. Screenshot. Georgetown Pike interchange with DRLT lanes
Figure 83. Illustration. DRLT design for a four-lane road with a single LT lane
Figure 84. Illustration. DRLT design for a four-lane road with dual LT lanes
Figure 85. Illustration. DRLT design for a six-lane road with dual LT lanes
Figure 86. Illustration. Proposed single-lane DRLT signalization during peak-period green phases
Figure 87. Illustration. Proposed single-lane DRLT signalization during off-peak-period green phases
Figure 88. Illustration. Proposed single-lane DRLT signalization during red phases for all periods
Figure 89. Illustration. DMSs for dual DRLT lanes during peak and off-peak periods
Figure 90. Illustration. Signal phasing and ring structure for proposed DRLT diamond interchanges
Figure 91. Equation. Calculation of DRLT signal TCL
Figure 92. Photo. Upstream advance warning sign for DRLT
Figure 93. Map. Example of no re-entry signage
Figure 94. Illustration. CLT intersection geometry
Figure 95. Illustration. Turn movement volumes at Tuckerman Lane and Rockville Pike in Maryland
Figure 96. Graph. Delay reductions due to CLT at various LT demand levels
Figure 97. Graph. Throughput increases due to CLT at various LT demand levels
Figure 98. Illustration. CLT pocket configuration
Figure 99. Illustration. Expected CLT lane utilization under low LT demand
Figure 100. Illustration. Expected CLT lane utilization under medium LT demand
Figure 101. Illustration. Expected CLT lane utilization under high LT demand
Figure 102. Equation. 95th percentile queue length
Figure 103. Equation. 95th percentile back-of-queue factor
Figure 104. Illustration. Side-swipe risk between CLTs and adjacent RTs
Figure 105. Illustration. Presignal at CLT pocket entrance
Figure 106. Illustration. Proposed CLT signalization during peak period
Figure 107. Illustration. Proposed CLT signalization during off-peak period
Figure 108. Illustration. CLT pocket signalization
Figure 109. Illustration. CLT intersection geometry
Figure 110. Equation. Calculation of CLT signal TCL for clearing the turn pocket
Figure 111. Equation. Calculation of CLT signal TCL for ensuring safe pocket entry
Figure 112. Equation. Truncated green time based on vehicle clearance
Figure 113. Equation. Truncated green time based on original green time
Figure 114. Map. CLT implementations in China
Figure 115. Photo. CLT intersection in China before the presignal has turned green
Figure 116. Photo. CLT intersection in China after the presignal has turned green but before the main signal has turned green
Figure 117. Photo. CLT intersection in China after the main signal has turned green

LIST OF TABLES

Table 1. Selected FHWA bottleneck relief sources
Table 2. New concepts affecting bottleneck rankings
Table 3. Traffic bottleneck attributes
Table 4. Number of candidates selected in each network by four criteria
Table 5. Analysis of the flagged candidates
Table 6. DLG benefits for case study 1
Table 7. DLG benefits of case study 2
Table 8. WB turning movement counts at the Shady Grove intersection
Table 9. DMS capital and operating costs
Table 10. Freeway-to-freeway merge scenarios
Table 11. Freeway on-ramp merge scenarios for DMC
Table 12. Calibrated driving behavior parameters
Table 13. AVD saving by the DMC strategy (s)
Table 14. AVD savings by the DMC strategy (s)
Table 15. AVD savings by the DMC strategy (mainline lane closure) (s)
Table 16. AVD saving by the DMC strategy for two-lane by two-lane ramp closure (s)
Table 17. AVD saving by the DMC strategy (s)
Table 18. AVD savings by the DMC strategy (s)
Table 19. AVD (s) savings by the DMC strategy (four-lane freeway
Table 20. Geometric configurations for testing acceleration lane lengths
Table 21. Volume demands for testing acceleration lane lengths (three-lane configuration)
Table 22. Volume demands for testing acceleration lane lengths (four-lane configuration)
Table 23. Estimated annual cost savings for increased acceleration lane length
Table 24. HSR summary results
Table 25. HSR delay reductions
Table 26. Possible cost savings under various scenarios of HSR
Table 27. Summary results of reducing lane widths to add new lanes
Table 28. Additional results from reducing lane widths to add new lanes
Table 29. Case study simulation results for DRLT lanes
Table 30. Case study simulation results for CLT pockets
Table 31. Sensitivity analysis experimental design for CLT

LIST OF ABBREVIATIONS

AASHTO American Association of State Highway and Transportation Officials  
AIIR Alternative Intersection and Interchange Report  
ARM annual reliability matrix  
ATM active traffic management  
AVD average vehicle delay  
B/C benefit-cost  
BII Bottleneck Intensity Index  
C&S Colts Neck Road and Sunrise Valley Drive  
CBI Congestion and Bottleneck Identification  
CLT contraflow left turn  
CMS changeable message sign  
DDI diverging diamond interchange  
D.I.V.E. duration, intensity, variability, and extent  
DJC dynamic junction control  
DLG dynamic lane grouping  
DLT displaced left-turn intersection  
DLTI displaced left-turn interchange  
DMC dynamic merge control  
DMS dynamic message sign  
DRLT dynamic reversible left turn  
EB eastbound  
FHWA Federal Highway Administration  
FI fatal and injury  
GEH Geoffrey E. Havers  
GPS Global Positioning System  
HCM Highway Capacity Manual  
HOT high-occupancy toll  
HOV high-occupancy vehicle  
HSR hard shoulder running  
ITS intelligent transportation system  
LOS level of service  
LT left turn  
MUT median U-turn intersection  
NB northbound  
NHI National Highway Institute  
O&M operations and maintenance  
PCE passenger car equivalent  
PDO property damage only  
PeMS performance measurement system  
RCUT restricted crossing U-turn intersection  
R&S Reston Parkway and Sunrise Valley Drive  
RITIS Regional Integrated Transportation Information System  
RRMSE relative root mean square error  
RT right turn  
SB southbound  
SHRP2 Second Strategic Highway Research Program  
STM spatio-temporal matrix  
STOL Saxton Transportation Operations Laboratory  
TCL clearance time  
TFHRC Turner-Fairbank Highway Research Center  
TH through  
TMC traffic message channel  
TTI Texas A&M Transportation Institute  
USDOT U.S. Department of Transportation  
v/c volume/capacity  
VDOT Virginia Department of Transportation  
v/l volume/lane  
VSL variable speed limit  
WB westbound  
WisDOT Wisconsin Department of Transportation  

 

 

 

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