Principles and Guidance for Presenting Active Traffic Management Information to Drivers (2021)

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C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR NCHRP WEB-ONLY DOCUMENT 286 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs B. Ray Derr, Senior Program Officer Anthony Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Jennifer Correro, Assistant Editor NCHRP PROJECT 03-124 PANEL Field of Traffic—Area of Operations and Control Gene S. Donaldson, Delaware Department of Transportation, Smyrna, DE (Chair) Ingrid L. Birenbaum, Moffat & Nichol, Fort Lauderdale, FL Joel Cooper, Red Scientific Inc, Salt Lake, UT Neal R. Hawkins, Iowa State University, Ames, IA Reza Karimvand, Arizona Department of Transportation, Phoenix, AZ Mubeen S. Quadri, Ohio Department of Transportation, Columbus, OH Brian Philips, FHWA Liaison Richard A. Cunard, TRB Liaison

i Table of Contents CHAPTER 1: INTRODUCTION ............................................................................................................... 6 OVERVIEW OF THE REPORT ................................................................................................................................... 7 CHAPTER 2: STATE OF THE PRACTICE ............................................................................................. 8 USE OF SYMBOLS IN ATM DEPLOYMENTS AND THE MANUAL OF UNIFORM TRAFFIC CONTROL DEVICES ..................................................................................................................................................................................... 8 MULTI-PURPOSE OVERHEAD LANE USE CONTROL SIGN DEPLOYMENTS ................................................... 10 DYNAMIC LANE CONTROL AND DYNAMIC LANE REVERSAL .......................................................................... 19 DYNAMIC SHOULDER LANE DEPLOYMENTS ..................................................................................................... 20 DYNAMIC SPEED LIMIT DEPLOYMENTS ............................................................................................................ 24 DYNAMIC JUNCTION CONTROL DEPLOYMENTS ............................................................................................... 33 DYNAMIC MERGE CONTROL DEPLOYMENTS .................................................................................................... 34 DYNAMIC QUEUE WARNING DEPLOYMENTS ................................................................................................... 35 STATIC SIGNAGE IN ADVANCE OF ATM DEPLOYMENTS ................................................................................ 36 INTERNATIONAL ATM DEPLOYMENTS ............................................................................................................. 39 IN-VEHICLE ATM MESSAGING ........................................................................................................................... 42 CHAPTER SUMMARY ............................................................................................................................................. 45 CHAPTER 3: LITERATURE REVIEW ................................................................................................ 46 METHODS FOR THE LITERATURE SEARCH ........................................................................................................ 46 LITERATURE SYNTHESIS ...................................................................................................................................... 48 CONCLUSIONS ........................................................................................................................................................ 50 CHAPTER SUMMARY ............................................................................................................................................. 51 CHAPTER 4: RESEARCH GAPS ........................................................................................................... 53 OVERVIEW .............................................................................................................................................................. 53 RESEARCH GAP DESCRIPTIONS .......................................................................................................................... 53 CONCLUSIONS ........................................................................................................................................................ 58 CHAPTER SUMMARY ............................................................................................................................................. 58 CHAPTER 5: EMPIRICAL STUDIES ................................................................................................... 60 GENERAL APPROACH TO EXPERIMENTS 1 AND 2 ............................................................................................ 61 EXPERIMENT 1: EVALUATING THE EFFECTS OF INFORMATION AVAILABILITY OF DYNAMIC LANE CONTROL ON DRIVER BEHAVIOR AND DISTRACTION ..................................................................................... 67 EXPERIMENT 1 SUMMARY ................................................................................................................................... 88 EXPERIMENT 2: EVALUATING THE EFFECTS OF INFORMATION MODALITY AND INFORMATION TYPE OF DYNAMIC SPEED LIMIT DISPLAYS ON DRIVER BEHAVIOR AND DISTRACTION. .......................................... 89 EXPERIMENT 2 SUMMARY ................................................................................................................................ 105 EXPERIMENT 3: EXAMINING HOW AGENCIES APPROACH THE DEPLOYMENT AND EVALUATION OF EXPERIMENT 3 SUMMARY ................................................................................................................................ 116 CHAPTER 6: CONCLUSIONS ............................................................................................................. 117 DESIGN GUIDELINES .......................................................................................................................... 122 APPENDICES ......................................................................................................................................... 131 APPENDIX A: FULL INTERVIEW RESPONSES & FOLLOW-UP SURVEY RESULTS .................................. 132 APPENDIX B: LIST OF DATA SOURCES GIVEN IN-DEPTH REVIEWS ....................................................... 166 APPENDIX C: RESEARCH QUESTION EVALUATION SURVEY .................................................................... 168 APPENDIX D: RESEARCH GAP CONSENSUS SCORES AND NOTES ............................................................ 173 APPENDIX E: REFERENCES ........................................................................................................................... 176

ii List of Tables TABLE 1. OVERHEAD DYNAMIC LANE CONTROL SIGNAGE DEPLOYMENTS AND ACCOMPANYING STRATEGIES IN THE UNITED STATES. .................................................................................................................................................................... 12 TABLE 2. CURRENT AND PLANNED DYNAMIC SHOULDER LANE DEPLOYMENTS IN THE UNITED STATES. ......................... 21 TABLE 3. CURRENT, PLANNED, AND DISCONTINUED DYNAMIC SPEED LIMIT DEPLOYMENTS IN THE UNITED STATES. .. 26 TABLE 4. URBAN AND CONGESTION DYNAMIC SPEED LIMIT DEPLOYMENTS IN THE UNITED STATES. ............................... 29 TABLE 5. WEATHER DYNAMIC SPEED LIMIT DEPLOYMENTS IN THE UNITED STATES. ......................................................... 31 TABLE 6. SELECT DYNAMIC SPEED LIMIT DEPLOYMENTS IN WORK ZONES. ............................................................................ 32 TABLE 7. TEMPORARY DYNAMIC QUEUE WARNING SYSTEM DEPLOYMENTS IN THE UNITED STATES. .............................. 36 TABLE 8. INTERNATIONAL ATM STRATEGY DEPLOYMENTS. .................................................................................................... 39 TABLE 9. PHOTOS OF INTERNATIONAL ATM STRATEGY SIGNAGE. .......................................................................................... 41 TABLE 10: RESEARCH SYNTHESIS MATRIX. ................................................................................................................................. 52 TABLE 11: DEFINITIONS FOR RATING WITHIN THE THREE SCALES. ........................................................................................ 56 TABLE 12. LIST OF THE KEY RESEARCH QUESTIONS AND CORRESPONDING RESEARCH GAPS. ............................................. 57 TABLE 13: FINAL SCORES FOR THE 13 RESEARCH GAPS. ........................................................................................................... 57 TABLE 14: OVERVIEW OF THE THREE EXPERIMENTS AND RESEARCH GAPS. ......................................................................... 60 TABLE 15. DATA SOURCES FOR ADDRESSING RESEARCH GAPS IN EXPERIMENT 1. ............................................................... 68 TABLE 16. SOURCES OF ATM INFORMATION FOR EACH EXPERIMENTAL CONDITION. ......................................................... 69 TABLE 17. PERCENTAGE OF TIME SPENT IN MERGE/CLOSE LANES. ........................................................................................ 72 TABLE 19. DATA SOURCES FOR ADDRESSING GAPS IN EXPERIMENT 2. ................................................................................... 90 TABLE 20. SOURCES OF ATM INFORMATION, INFORMATION MODALITY, AND AVAILABILITY OF PRESCRIPTIVE WARNING FOR EACH EXPERIMENTAL CONDITION. ............................................................................................................................. 91 TABLE 21. PERCENTAGE OF SPEED COMPLIANCE AND AVERAGE SPEED EXCEEDANCE BY EXPERIMENTAL CONDITIONS. ................................................................................................................................................................................................. 93 TABLE 22. SUMMARY GLANCE STATISTICS FOR EXPERIMENT 2. .............................................................................................. 96 TABLE 23. STAKEHOLDERS SURVEYED AND/OR INTERVIEWED FOR EXPERIMENT 3 ....................................... 96 TABLE 24. DEPLOYMENT OF ATM STRATEGIES AMONG RESPONDENTS’ AGENCIES. ......................................................... 112 List of Figures FIGURE 1. PROJECT SEQUENCE AND TASKS. .................................................................................................................................... 7 FIGURE 2. ATM LANE CONTROL DISPLAYS USED BY DIFFERENT DEPLOYMENT SITES TO CONVEY INFORMATION TO DRIVERS (WSDOT, MNDOT, CDOT, CALTRANS, VDOT). ............................................................................................ 9 FIGURE 3. DYNAMIC SPEED LIMIT SIGNS IN MAINE, LEFT, AND OREGON, RIGHT (FHWA, OREGON DOT). .................... 10 FIGURE 4. LANE USE CONTROL SIGNAGE ON I-80 IN THE BAY AREA (CALTRANS). .............................................................. 13 FIGURE 5. LANE USE CONTROL SIGNAGE ON US 36 IN DENVER (GOOGLE MAPS). ............................................................... 13 FIGURE 6. LANE USE CONTROL SIGNAGE ON I-25 SOUTHBOUND IN DENVER (GOOGLE MAPS). ......................................... 14 FIGURE 7. LANE USE CONTROL SIGNAGE ON THE I-295 DELAWARE MEMORIAL BRIDGE (GOOGLE MAPS). ................... 14 FIGURE 8. LANE USE CONTROL SIGNAGE ON THE I-90 TOLLWAY NORTHWEST OF CHICAGO (DAILY HERALD). ............. 15 FIGURE 9. LANE USE CONTROL SIGNAGE ON I-93 IN BOSTON (GOOGLE MAPS). .................................................................. 15 FIGURE 10. LANE USE CONTROL SIGNAGE ON I-35W IN MINNEAPOLIS (GOOGLE MAPS). ................................................. 16 FIGURE 11. LANE USE CONTROL SIGNAGE ON I-94 IN MINNEAPOLIS (FHWA). .................................................................. 16 FIGURE 12. LANE USE CONTROL SIGNAGE ON US 290 IN AUSTIN (GOOGLE MAPS). ........................................................... 16 FIGURE 13. LANE USE CONTROL SIGNAGE ON I-66 IN NORTHERN VIRGINIA (VIRGINIA DOT). ........................................ 17 FIGURE 14. LANE USE CONTROL SIGNAGE ON I-66 IN NORTHERN VIRGINIA (VIRGINIA DOT). ........................................ 17 FIGURE 15. LANE USE CONTROL SIGNAGE ON I-5 IN SEATTLE (GOOGLE MAPS). ................................................................. 18 FIGURE 16. LANE USE CONTROL SIGNAGE ON I-5 IN SEATTLE (WSDOT). ........................................................................... 18 FIGURE 17. ARTERIAL LANE CONTROL SIGNS ON 5400 SOUTH IN SALT LAKE CITY, UTAH (SALT LAKE CITY TRIBUNE). .............................................................................................................................................................................. 19 FIGURE 18. ARTERIAL LANE CONTROL SIGNS IN MONTGOMERY COUNTY, MARYLAND (MONTGOMERY COUNTY DOT). ................................................................................................................................................................................................. 19

iii FIGURE 19. LANE REVERSAL DEPLOYMENT ON I-595 HOT LANES IN MIAMI (SUN SENTINEL). ..................................... 20 FIGURE 20. LANE REVERSAL DEPLOYMENT ON I-5 HOV LANES IN SEATTLE (GOOGLE MAPS). ....................................... 20 FIGURE 21. DYNAMIC SHOULDER LANE ON I-70 EAST IN COLORADO (GOOGLE MAPS). .................................................... 20 FIGURE 22. DYNAMIC SHOULDER LANE ON I-85 NORTH NEAR ATLANTA (GOOGLE MAPS). ............................................. 21 FIGURE 23. DYNAMIC SHOULDER LANE ON I-35W NORTH IN MINNEAPOLIS (MINNESOTA DOT). ................................. 22 FIGURE 24. DYNAMIC SHOULDER LANE ON THE I-78 NEW JERSEY TURNPIKE IN NEWARK (FHWA). ............................ 22 FIGURE 25. DYNAMIC SHOULDER LANE ON I-66 IN NORTHERN VIRGINIA (GOOGLE MAPS). ............................................ 23 FIGURE 26. PREVIOUS STATIC TIME OF DAY SHOULDER LANE ON I-66 IN NORTHERN VIRGINIA (FHWA). ................... 23 FIGURE 27. DYNAMIC SHOULDER LANE ON I-495 NORTH IN NORTHERN VIRGINIA (GOOGLE MAPS). ........................... 24 FIGURE 28. DYNAMIC JUNCTION CONTROL ON THE SR 110 ARROYO SECO PARKWAY IN LOS ANGELES (FHWA). ..... 33 FIGURE 29. DYNAMIC JUNCTION CONTROL ON I-94 IN MINNEAPOLIS DISPLAYING GUIDE SIGNS FOR AN EXIT WITH AND WITHOUT AN EXIT ONLY LANE DESIGNATION (GOOGLE MAPS). ................................................................................... 33 FIGURE 30. EXAMPLE OF A DYNAMIC MERGE CONTROL APPLICATION ENCOURAGING A LATE MERGE; TOP PHOTOS SHOW THE TWO-PHASE MESSAGE DISPLAYED ON THE FIRST PORTABLE DMS AND BOTTOM PHOTOS SHOW THE TWO-PHASE MESSAGE ON THE PORTABLE DMS LOCATED AT THE MERGE POINT (INTERNATIONAL ROAD DYNAMICS). ................................................................................................................................................................................................. 34 FIGURE 31. DYNAMIC MERGE CONTROL TO ENCOURAGE A LATE MERGE AT A WORK ZONE IN MINNESOTA (MINNESOTA DOT). ..................................................................................................................................................................................... 35 FIGURE 32. TYPICAL, TEMPORARY DYNAMIC QUEUE WARNING SYSTEM DEPLOYED FOR A WORK ZONE ON I-35 IN CENTRAL TEXAS (TEXAS A&M TRANSPORTATION INSTITUTE)................................................................................... 36 FIGURE 33. STATIC SIGN IN ADVANCE OF DYNAMIC SPEED LIMITS ON SR 520 IN SEATTLE (GOOGLE). ........................... 37 FIGURE 34. STATIC SIGN IN ADVANCE OF TEMPORARY DYNAMIC SPEED LIMITS IN A WORK ZONE ON I-495 IN VIRGINIA (VIRGINIA DOT). .................................................................................................................................................................. 37 FIGURE 35. STATIC SIGN IN ADVANCE OF DYNAMIC SPEED LIMITS ON I-270 IN ST. LOUIS (AAROADS.COM) ................. 38 FIGURE 36. STATIC SIGN IN ADVANCE OF DYNAMIC SPEED LIMITS ON US 27 IN FORT LAUDERDALE (AAROADS.COM) 38 FIGURE 37. STATIC SIGN TO EXPLAIN FORMER DYNAMIC SHOULDER LANE SYMBOLS AND HOURS ON I-66 IN NORTHERN VIRGINIA (FHWA). .............................................................................................................................................................. 38 FIGURE 38. STATIC SIGN TO EXPLAIN LANE CONTROL SYMBOLS CURRENTLY IN USE ON I-66 IN NORTHERN VIRGINIA (VIRGINIA DOT). .................................................................................................................................................................. 38 FIGURE 39. STATIC SIGN TO EXPLAIN DYNAMIC SHOULDER LANE SYMBOLS ON I-495 IN NORTHERN VIRGINIA (GOOGLE MAPS). .................................................................................................................................................................................... 39 FIGURE 40. STATIC SIGN TO EXPLAIN DYNAMIC SHOULDER LANE SYMBOLS ON I-85 NEAR ATLANTA (GOOGLE MAPS). ................................................................................................................................................................................................. 39 FIGURE 41. PICTOGRAM DISPLAY OF DYNAMIC LANE CONTROL AND DYNAMIC SPEED LIMIT IN THE UNITED KINGDOM (TRAFFIC TECHNOLOGY INTERNATIONAL). ..................................................................................................................... 40 FIGURE 42. IN-VEHICLE DISPLAY FOR INC-ZONE DYNAMIC MERGE CONTROL AND DYNAMIC SPEED LIMIT APPLICATIONS DURING CLOSED FIELD TEST DEMONSTRATION IN MARYLAND (BATTELLE). .................................. 44 FIGURE 43. IN-VEHICLE DISPLAY FOR INFLO DYNAMIC QUEUE WARNING AND DYNAMIC SPEED LIMIT APPLICATIONS DURING DEMONSTRATION TEST IN SEATTLE ON I-5 NORTH (BATTELLE). ................................................................. 44 FIGURE 44. A SMARTPHONE WAS USED AS AN IN-VEHICLE DISPLAY OF INFORMATION DURING THE INC-ZONE AND INFLO DEMONSTRATIONS (BATTELLE). .......................................................................................................................... 44 FIGURE 45: OVERVIEW OF LITERATURE REVIEW ACTIVITIES. ................................................................................................ 46 FIGURE 46. SAMPLE DOCUMENT SUMMARY TEMPLATE (ADAPTED FROM MCCALLUM ET AL., 2006). ........................... 48 FIGURE 47: FINAL SCORES OF THE 13 RESEARCH GAPS IN THREE DIMENSIONS (COLOR REPRESENTS EXPECTED METHODS TO CONDUCT STUDIES). ...................................................................................................................................... 58 FIGURE 48. THE SMARTPHONE WAS LOCATED TO THE RIGHT OF THE STEERING WHEEL. ................................................... 63 FIGURE 49. A SCREEN CAPTURE FROM THE SMARTPHONE APPLICATION. .............................................................................. 64 FIGURE 50. ERGONEERS HEAD-MOUNTED EYE-TRACKER. ........................................................................................................ 65 FIGURE 51. MANUALLY DEFINED AOI (BLUE BOX) AND DRIVERS’ FIXATION POINT (RED CROSSED CIRCLE) CAPTURED FROM THE D-LAB SOFTWARE. ............................................................................................................................................ 65 FIGURE 52. ROAD LAYOUT FOR EXPERIMENT 1. ......................................................................................................................... 70 FIGURE 53. LANE SIGNAL SYMBOLS. .............................................................................................................................................. 71 FIGURE 54. A SAMPLE IMAGE OF OVERHEAD GANTRY WITH LANE CLOSURE SIGNS FROM EXPERIMENT 1. ...................... 71 FIGURE 55. PROVISIONAL SIGNS (HIGHLIGHTED IN RED BOXES) FROM EXPERIMENT 1. ..................................................... 71 FIGURE 56. PERCENTAGE OF TIME IN MERGE/CLOSE LANES. ................................................................................................... 73

iv FIGURE 58. MEAN GLANCE TIME TO THE SMARTPHONE IN SECONDS. ..................................................................................... 76 FIGURE 59. RATINGS FOR IMPORTANCE OF EACH ATM APPLICATION’S PURPOSE................................................................ 77 FIGURE 60. RATINGS FOR USEFULNESS OF EACH ATM APPLICATION. .................................................................................... 77 FIGURE 61. RATINGS FOR HOW WELL EACH ATM APPLICATION COMMUNICATES. .............................................................. 78 FIGURE 62. RATINGS FOR LEVEL OF COMPREHENSION OF SYMBOLS USED IN EACH ATM APPLICATION. ......................... 78 FIGURE 63. USEFULNESS RATINGS FOR OVERHEAD MOUNTED SIGN AND SMARTPHONE ATM APPLICATIONS. ............... 79 FIGURE 64. PREFERENCE RATINGS FOR OVERHEAD MOUNTED SIGNS AND SMARTPHONE ATM APPLICATIONS. ............ 79 FIGURE 65. PREFERENCE RATINGS FOR ALL ATM APPLICATIONS. .......................................................................................... 79 FIGURE 66. PREFERENCE RATING FOR EACH ATM PRESENTATION MODE. ........................................................................... 80 FIGURE 67. PARTICIPANTS’ TIMING ASSESSMENT OF THE SMARTPHONE APPLICATION IN JUST-IN-TIME MODE. ............ 81 FIGURE 68. BOXPLOTS OF PARTICIPANTS RESPONSES ON THEIR STRATEGY TO USE BOTH ATM MEDIA. ......................... 81 FIGURE 69. DISTRACTION RATINGS FOR SIGN PRESENTATION BY SMARTPHONE APPLICATION MODE. ............................. 82 FIGURE 70. ANNOYANCE RATINGS FOR SIGN PRESENTATION BY SMARTPHONE APPLICATION MODE. ............................... 82 FIGURE 71. OVERALL DISTRACTION RATINGS FOR THE SMARTPHONE APPLICATION. .......................................................... 82 FIGURE 72. PARTICIPANTS’ SELF-REPORTED LIKELINESS TO USE THE SMARTPHONE APPLICATION TO RECEIVE ATM INFORMATION IN THE FUTURE. ........................................................................................................................................... 83 FIGURE 73. PERCENTAGE OF PARTICIPANTS WHO NOTICED REDUCED SPEED ZONE SIGN. .................................................. 83 FIGURE 74. PARTICIPANTS’ SELF-REPORTED EFFECTIVENESS OF THE PROVISIONAL SIGNS. ............................................... 83 FIGURE 75. EXAMPLES OF PROVISIONAL SIGNS PRESENTED TO PARTICIPANTS. .................................................................... 84 FIGURE 76. IMPORTANCE RATINGS FOR PROVISIONAL SIGNS. .................................................................................................. 85 FIGURE 77. EFFECTIVENESS RATINGS FOR PROVISIONAL SIGNS. .............................................................................................. 85 FIGURE 78. EASE OF UNDERSTANDING RATINGS FOR PROVISIONAL SIGNS. ............................................................................ 85 FIGURE 79. ROAD LAYOUT FOR EXPERIMENT 2. ......................................................................................................................... 92 FIGURE 80. SAMPLE IMAGE OF DYNAMIC SPEED LIMIT INFORMATION PRESENTED ON GANTRIES FOR EXPERIMENT 2. 93 FIGURE 81. PERCENTAGE OF SPEED COMPLIANCE. ..................................................................................................................... 94 FIGURE 82. SPEED EXCEEDANCE.................................................................................................................................................... 95 FIGURE 83. TOTAL GLANCE TIME TO THE SMARTPHONE ACROSS EXPERIMENTAL CONDITIONS. ........................................ 97 FIGURE 84. MEAN GLANCE TIME TO SMARTPHONE ACROSS EXPERIMENTAL CONDITIONS. ................................................. 97 FIGURE 85. PARTICIPANTS’ SUBJECTIVE RATINGS OF EFFECTIVENESS FOR THREE TYPES OF ATM MEDIA. ..................... 99 FIGURE 86. PARTICIPANTS’ RATINGS FOR HOW WELL THREE TYPES OF ATM MEDIA COMMUNICATE. .......................... 100 FIGURE 87. PARTICIPANTS’ RELATIVE RATINGS OF EFFECTIVENESS FOR THREE ATM MEDIA BY ROAD TYPE. ............. 101 FIGURE 88. PARTICIPANTS’ RELATIVE RATINGS OF EFFECTIVENESS FOR FIVE ATM STRATEGIES BY ROAD TYPE. ....... 101 FIGURE 89. PARTICIPANTS’ RATINGS FOR USEFULNESS AND PREFERENCE BETWEEN OVERHEAD SIGNS AND SMARTPHONE APPLICATION AS ATM MEDIA. ............................................................................................................... 102 FIGURE 90. PARTICIPANTS’ COMPARISONS OF THE THREE ATM PRESENTATION MODES IN EXPERIMENT 2. .............. 103 FIGURE 91. DISTRACTION RATINGS FOR THE THREE SMARTPHONE APPLICATION MODES IN EXPERIMENT 2. ............. 103 FIGURE 92. PARTICIPANTS’ PREFERRED WAY TO RECEIVE NAVIGATION INSTRUCTIONS. ................................................. 104 FIGURE 93. PARTICIPANTS’ SELF-REPORTED LIKELINESS TO USE THE SMARTPHONE APPLICATION TO RECEIVE ATM INFORMATION IN THE FUTURE. ........................................................................................................................................ 104

v List of Acronyms and Abbreviations AASHTO ................ American Association of State Highway and Transportation Officials ADT ................................................................................................... Average Daily Traffic AOI .............................................................................................................. Area of Interest ATIS ....................................................................... Advanced Traveler Information System BES ................................................................................................ Best Evidence Synthesis CR ................................................................................................................. Contrast Ratios DOT ....................................................................................... Department of Transportation DMS .................................................................................................Dynamic Message Sign HFG............................................................................................. Human Factors Guidelines HPS ................................................................................................... High-Pressure Sodium IHSDM ............................................................... Interactive Highway Safety Design Model IVIS ..................................................................................... In-vehicle Information Systems LCS ......................................................................................................Lane Control Signals LED ..................................................................................................... Light Emitting Diode MUTCD ......................................................... Manual on Uniform Traffic Control Devices NCHRP ................................................. National Cooperative Highway Research Program NLT .................................................................................................................. No Left Turn NRT................................................................................................................ No Right Turn PCC ............................................................................................. Portland Cement Concrete PCMS ............................................................................ Portable Changeable Message Sign RRPM ........................................................................ Raised Reflective Pavement Marking RSI ............................................................................... Level of Reported Sign Information RT .................................................................................................................. Reaction Time SAFETEA-LU Safe, Accountable, Flexible, Efficient Trans. Equity Act: Legacy for User SRS ................................................................................................... Shoulder Rumble Strip SUV...................................................................................................... Sport Utility Vehicle SVB ......................................................................................................... Slow Vehicle Bays SVROR ..................................................................................Single Vehicle Run-Off-Road SYG..................................................................................................... Strong Yellow-Green TIM ....................................................................................... Tactical Incident Management TMC .......................................................................................... Traffic Management Center TTC ........................................................................................................... Time-to-Collision VMS ................................................................................................ Variable Message Signs

vi VPD............................................................................................................ Vehicles Per Day VSL ..................................................................................................... Variable Speed Limit USSC.......................................................................................... United States Sign Council

1 Summary Active Traffic Management (ATM) strategies have become more common in the United States as State departments of transportation (DOTs) grapple with increasing congestion and fewer dollars available to add capacity to keep pace. ATM strategies provide a more cost-effective solution to better manage traffic using the available capacity of the existing roadway network. The expansion of ATM strategies and implementations has led to a concurrent increase in the options available to deliver ATM information to drivers. Information displays designed to capture drivers’ attention quickly include devices that vary in terms of whether they are: fixed and moveable, graphics-based and text-based, overhead and roadside, as well as handheld and vehicle-based. Because of the innovative nature of ATM strategies, there is limited guidance available and many research questions remain about how ATM information can be effectively and safely presented to drivers across the many existing and potential dissemination methods. The objective of this project is to develop principles and guidance for presenting drivers with dynamic information that can be frequently updated based on real-time conditions. These principles and guidance should improve the effectiveness of ATM strategies, which include systems to manage congestion, incidents, weather, special events, and work zones. The project is intended to explore and provide answers to the following six key research questions: 1. What information related to ATM strategies does a driver want and need? What characteristics are associated with this information (e.g., reliability, timeliness)? 2. How much information can a driver process via the complementary and contrasting modalities (e.g., visual, auditory), given the context and distractions? 3. What existing and potential media could be used to deliver this information? Media that are under the control of transportation agencies (e.g., electronic signs) are of primary interest but alternative and innovative media (e.g., in-vehicle displays, cell phone applications, geographic information systems) and their evolving capabilities and roles must be examined. 4. Given a particular message and medium, what are effective ways to prioritize, format, and present the information to achieve a desired and safe response by drivers? 5. How can an agency evaluate the return on investment of an ATM infrastructure or information technology decision? 6. How can an agency balance the needs of drivers and infrastructure costs, including maintenance and operations? This project involved two broad phases to achieve its goals. Phase 1 (Chapters 2-4) primarily involved documenting the ATM state of the practice and reviewing critical literature, with the goal of specifying the detailed requirements of the Phase 2 research and analysis activities. Phase 2 of the project (Chapters 5-6) involved original research and data analysis to inform the development of a series of deliverables including guidance and principles for agencies and third- party providers on the presentation of ATM information to drivers. This report is divided into six chapters: • Chapter 1 – Introduction: This chapter provides a general overview of the project objectives • Chapter 2 – State of the Practice: This chapter documents the state of the current practice of displaying ATM information both within the United States and internationally

2 • Chapter 3 – Literature Review: This chapter synthesizes the available literature about displaying ATM information in key topic areas and identifies research gaps within those topics • Chapter 4 – Research Gaps: This chapter describes activities related to refining and prioritizing research gaps related displaying ATM information • Chapter 5 – Empirical Studies: This chapter describes the methodology and findings for three studies that were conducted during this project to address the key research gaps • Chapter 6 – Conclusions: This chapter integrates the available information about each research gap developed across all project activities To develop principles and guidance for presenting ATM information, different activities were conducted in both qualitative and quantitative ways. The key activities are described below. The objective of the State of Practice review was to identify and document ATM deployments in the United States, as well as available guidance from the Manual of Uniform Traffic Control Devices (MUTCD). The review collected descriptions and photos of permanent and temporary ATM systems in 27 states, including deployments of multipurpose overhead lane use control signs, dynamic lane control and dynamic lane reversal, dynamic shoulder lanes, dynamic speed limits, dynamic junction control, dynamic merge control, and dynamic queue warning. ATM applications in work zones were also documented, as well as the types of static signage placed in advance of ATM deployments. Additionally, international ATM deployments and existing in- vehicle ATM messaging approaches are also documented. The State of Practice review provided important context to the broader project by highlighting the variations in ATM deployments, and thus the need for additional research and guidance for presenting dynamic ATM information to drivers. Along with the State of Practice review, a literature review was conducted to synthesize recent and relevant findings. A literature search was conducted using both broad search and focused search processes. A total of 404 articles were searched, and 26 of those articles went through a structured, in-depth review. The literature review identified a number of data sources that provided general design guidance for ATM messages. However, practical answers to key research questions 1-4 were not provided by the existing literature. The output of the literature review was used to identify key research gaps and develop research questions for the Phase 2 activities. The findings from the literature review and State of Practice provided inputs to structured research gap analysis that was conducted to refine and prioritize the research needs that could be addressed in the project. The literature review and State of Practice generated 13 research gaps focusing on how the evolving alternative information channels could impact the role of DOT infrastructure and messaging practices. After identifying the 13 research gaps, three subject matter experts individually rated each research gap along five-point scales using three criteria: (a) relevance, (b) usefulness, and (c) expected cost. After all ratings were finalized, overall priority scores were calculated for each research gap. Following the initial evaluation of the 13 research gaps, the project team conducted further discussions and received input on the gaps from a State DOT stakeholder group and the NCHRP project panel. Two research gaps were excluded because they were not highly relevant or feasible. To address the remaining 11 research

3 gaps, two driving simulator studies and a separate stakeholder engagement study were conducted. The first driving simulator study investigated the effects of the availability of the ATM information on driver behavior and distraction. The study focused on a dynamic lane signaling application and compared drivers’ behavior under two levels of information availability (“always-on” mode, which displayed the lane closure information always vs. “just-in-time” mode, which displayed the information only when a vehicle was near a corresponding overhead gantry) for smartphone ATM applications. Drivers were more likely to follow the lane closure information when they received the information from both the smartphone and overhead gantry at the same time, compared to when they received the information only from the overhead gantries. In addition, when the ATM information was available from both the smartphone and overhead gantry, there were no significant differences between the two levels of information availability on drivers’ compliance of lane closure information. However, the post-experiment survey showed that 70% of the participants preferred the “always-on” mode over the “just-in- time” mode. An analysis of driver glances showed that total glance time and average glance duration to the smartphone in the study were below the Alliance of Automobile Manufacturers (AAM)’s distraction criterion for human-machine interface interaction. The average glance duration to the smartphone was around 0.5 seconds. The results indicated that disseminating the ATM information via the smartphone along with the navigation information did not cause additional visual distraction. Given the sample size (n = 44) and limitations of the driving simulator study, differences observed in the study were too small to have practical significance. However, the study simulated situations in which ATM information can be disseminated from alternative ATM media and/or traditional ATM media, and it provided useful information about how to effectively use alternative media for ATM message dissemination in conjunction with infrastructure-based media. The output of the study was used to develop design guidelines and recommendations. The second driving simulator study investigated the effects of information modality (visual symbols vs. visual symbols and auditory messages) and information type (descriptive auditory messages vs. prescriptive auditory warning) of in-vehicle ATM displays on driver behavior and distraction. The research questions were examined in the context of a dynamic speed limit application. Drivers were more likely to drive 5 mph above the speed limit when they received the dynamic speed limit information from only the smartphone compared the other conditions. The results showed that when the smartphone was the sole source of ATM information, drivers were more likely to drive above the speed limit. Although there were no significant differences between modality conditions or information type conditions, the post-experiment survey showed that 60% of the participants preferred both a combined auditory-visual modality and descriptive information for the smartphone ATM application. Similar to the first driving simulator study, an analysis of driver glances showed that total glance time and average glance duration to the smartphone in the study were below the AAM’s distraction criterion for human-mahine interface interaction in all conditions. However, providing visual speed limit information on the smartphone increased glances towards the application relative to when speed limit information was only available on the gantry (i.e., when

4 the smartphone only presented navigation information). This effect dimished when the the speed limit information on the smartphone was also presented as an auditory message in addition to the visual message. The results suggest that the addition of auditory messages enabled drivers to maintain the same focus on the driving task as they did when ATM information was only displayed on the infrastructure. The stakeholder engagement study was conducted to identify current and best practices used by agencies to effectively deploy and quantitatively evaluate the potential and realized benefits of various ATM strategies. Gaps within currently available guidelines and requirements were identified and guidance to support a transition to innovative, non-traditional media for presenting dynamic information was also investigated. This study relied on email communications, targeted web-based surveys and virtual telephone interviews, and a focus group to gather information from 13 transportation agencies about a variety of permanent and temporary ATM deployments. This study showed that most ATM deployment evaluations focus on travel time and delay measures to quantify mobility benefits, although mobility is not always considered since it can be challenging to quantify or may not be a focus of all ATM deployments. Evaluation approaches varied from a relatively simple before-after calculation of trends or statistical analysis of data to more complex modeling methodology or video analysis. Multiple evaluation reports are available to review methodology and findings in greater detail. Respondents with temporary ATM deployments in work zones noted challenges with evaluation due to the short duration and different conditions for each location. Many respondents struggled with defining how their agency balances driver needs versus safety, mobility, and costs for ATM deployments, with some interviewees saying they were not sure that their agencies fully understood “driver needs”. Survey responses showed varying responses, with nearly all agencies considering both mobility impacts and safety impacts for all types of ATM strategies, a large majority considering costs for all types of ATM strategies, and most considering driver needs for at least one type of ATM strategy. Regarding available ATM resources and gaps, peer exchanges and interactions with other agencies that have deployed ATM strategies were cited most frequently as the primary, and often best, resource. Respondents also noted a variety of Federal Highway Administration (FHWA) resources and the MUTCD. Respondents identified resource gaps in many topic areas, particularly message display, sign placement, and software and algorithm development for automated operations. In-vehicle messaging resources were not identified as a gap, perhaps in part due to agency liability concerns, limited testing and deployment, or reliance on the private sector or other non-agency partners to develop and facilitate the provision of in-vehicle messages. The research activities conducted in this project provided actionable information pertaining to several of the research gaps. However, because the studies targeted a broad set of research gaps, the resulting information did not address each research gap completely. Based on the findings, initial design guidelines and recommendations were generated. This information was presented as two separate “guidelines” that provided high-level design information target at ATM message developers. Each guideline included additional discussion and design issues developed based on the best-available information from the literature review and empirical activities.

5 Guideline 1 stated that: Alternative ATM media must be coordinated with the primary information provided by infrastructure-based ATM media. The following attributes support good use of traditional and alternative ATM media. • Alternative media should supplement, not replace infrastructure-based ATM media • Ensure that alternative ATM media information type and timing are consistent with the ones used in the infrastructure-based ATM messages • Use alternative ATM media to present persistent information continuously • The presentation timing of alternative ATM media should complement or match the time- course of infrastructure-based ATM messages • Coordinate onset timing of alternative ATM media to the legibility distance of infrastructure-based ATM media Guideline 2 stated that: When used to supplement traditional ATM media, an alternative ATM medium’s message modality, message type, and location should have characteristics that promote driver information retention and understanding, without causing distraction. • Use auditory-visual (AV) messages for alternative ATM media rather than visual-only messages o When providing auditory messages for dynamic speed limits, use descriptive messages and avoid prescriptive messages • Avoid using alternative ATM media as sole sources of ATM information • Different combinations of modalities suit different levels of complexity; match message modality to message complexity • In-vehicle displays should be in a location central to the driving task. Special accommodations should be made for smartphone displays Overall, ATM information dissemination is still an emerging topic that requires further research to establish best practices. Nevertheless, this project made significant strides toward framing the research gaps and addressing some of those information needs.

6 Chapter 1: Introduction ATM strategies have become more common in the United States, particularly in the last decade, as state DOTs grapple with increasing congestion and fewer dollars available to add capacity to keep pace. ATM strategies provide a more cost-effective solution to better manage traffic using the available capacity on the existing roadway network. The expansion of ATM strategies and implementation has led to a concurrent increase in the options available to deliver ATM information to drivers. Information displays designed to capture drivers’ attention quickly include devices that are: fixed and moveable, graphics-based and text-based, overhead and roadside, as well as handheld and vehicle-based. Because of the innovative nature of ATM strategies, there is limited guidance available and many research questions remain about how ATM information can be effectively and safely presented to drivers across the many existing and potential dissemination methods. The objective of project NCHRP 03-124 is to develop principles and guidance for presenting drivers with dynamic information that can be frequently updated based on real-time conditions. These principles and guidance should improve the effectiveness of ATM strategies, which include systems to manage congestion, incidents, weather, special events, and work zones. The project is intended to explore and provide answers to the following six key research questions: 1. What information related to ATM strategies does a driver want and need? What characteristics are associated with this information (e.g., reliability, timeliness)? 2. How much information can a driver process via the complementary and contrasting modalities (e.g., visual, auditory), given the context and distractions? 3. What existing and potential media could be used to deliver this information? Media that are under the control of transportation agencies (e.g., electronic signs) are of primary interest, but alternative and innovative media (e.g., in-vehicle displays, cell phone applications, geographic information systems) and their evolving capabilities and roles must be examined. 4. Given a particular message and medium, what are effective ways to prioritize, format, and present the information to achieve a desired and safe response by drivers? 5. How can an agency evaluate the return on investment of an ATM infrastructure or information technology decision? 6. How can an agency balance the needs of drivers and the infrastructure costs, including maintenance and operations? This report describes the activities and results associated with Task 9: Develop and Submit Deliverables. Figure 1 provides an overview of the project and individual tasks.

7 Figure 1. Project sequence and tasks. Overview of the Report This report is divided into six chapters. • Chapter 1 – Introduction: The current chapter, which provides a general overview of the project objectives • Chapter 2 – State of the Practice: This chapter documents the state of the practice of displaying ATM information both within the United States and internationally • Chapter 3 – Literature Review: This chapter synthesizes the available literature about displaying ATM information in key topic areas and identifies research gaps within those topics • Chapter 4 – Research Gaps: This chapter describes activities related to refining and prioritizing research gaps related displaying ATM information • Chapter 5 – Empirical Studies: This chapter describes the methodology and findings for three studies that were conducted during this project to address the key research gaps • Chapter 6 – Conclusions: This chapter integrates the available information about each research gap developed across all project activities

8 Chapter 2: State of the Practice A variety of ATM systems have been deployed in the United States and internationally. This section first presents guidance from the MUTCD. It is important to note that this effort excludes ATM deployments that use a standard traffic signal to present dynamic information to drivers (e.g., adaptive ramp metering, adaptive traffic signal control, and transit signal priority). Descriptions and photos of ATM systems in the United States are presented next, including: • Multi-Purpose Overhead Lane Use Control Sign Deployments; • Dynamic Lane Control and Dynamic Lane Reversal; • Dynamic Shoulder Lane Deployments; • Dynamic Speed Limit Deployments; • Dynamic Junction Control Deployments; • Dynamic Merge Control Deployments; and • Dynamic Queue Warning Deployments. Examples of Static Signage in Advance of ATM Deployments in the United States are also discussed, as well as descriptions of International ATM Deployments and existing In-Vehicle ATM Messaging. Documenting the state of practice by highlighting existing guidance for ATM deployments, and then presenting photos and descriptions of all identified ATM deployments in the United States and internationally, adds context to this effort by highlighting the variations in deployments and thus the needs for additional research and guidance for presenting dynamic ATM information to drivers. Use of Symbols in ATM Deployments and the Manual of Uniform Traffic Control Devices The MUTCD provides guidance in Chapter 4M on the use of lane control signals. Specifically, the following summarized guidance is provided for use of the following symbols in a steady mode, i.e., not flashing: • Downward Green Arrow: a road user is permitted to drive in the lane over which the arrow signal indication is located. • Yellow X: a road user is to prepare to vacate the lane over which the signal indication is located because a lane control change is being made to a red X signal indication. • Red X: a road user is not permitted to use the lane over which the signal indication is located and that this signal indication shall modify accordingly the meaning of other traffic controls present. • White Two-Way Left-Turn Arrow: a road user is permitted to use a lane over which the signal indication is located for a left turn, but not for through travel, with the understanding that common use of the lane by oncoming road users for left turns is also permitted. • White One-Way Left-Turn Arrow: a road user is permitted to use a lane over which the signal indication is located for a left turn (without opposing turns in the same lane), but not for through travel.

9 Usage of these symbols is generally consistent on ATM lane use signage in the United States, although some locations use text instead of a yellow X to indicate that a lane is closed ahead, as shown in Figure 2. To minimize driver confusion, some locations also display text to accompany symbols. Washington State DOT previously used a yellow X symbol with a distance text underneath but found it to be less effective than the diagonal merge symbols and no longer uses it. Note that the Minnesota DOT sometimes uses a yellow X with text “1 mile” underneath instead of the text “lane closed ahead,” but only for a one-mile distance. Figure 2. ATM lane control displays used by different deployment sites to convey information to drivers (WSDOT, MnDOT, CDOT, Caltrans, VDOT). Additionally, all known freeway applications of lane control signs in the United States have a blank sign for default conditions when there is no message to display, as permitted by the MUTCD. However, freeway applications of ATM lane control also display additional information like a caution message, merge, or a variable speed, as depicted in Figure 2. These additional uses are typically based on guidance provided in the MUTCD for other uses, such as the display of speed limits on a static sign or merging chevron arrows used for a work zone arrow board. Some symbols were implemented following the submission and approval of a request to experiment to FHWA, given the variation from the MUTCD guidance. Regulatory dynamic speed limit signs follow MUTCD guidance as black on white or white on black displays in a typical configuration, as seen on static signage. However, the way they are displayed can vary based on the coloration and extent of the dynamic element and the display technology, i.e., a static sign with dynamic numbers versus a fully digital sign. Advisory dynamic speeds are less consistent in how they are displayed to drivers. Advisory dynamic speeds are generally based on MUTCD guidance in that they are yellow and black and often / LOCATION WA: I-90, I-5, SR 520 2 + ONLY CAUTION MN: I-94, I-35W CO: I-25, US 36 CA: I-80 VA: I-66

10 based on a static advisory speed sign that might be placed at a curve, for example. Figure 2 and Figure 3 show variations in how advisory speeds are displayed to drivers on dynamic signs. Additional display examples will be exhibited below in Dynamic Speed Limit Deployments. The use of symbols (or not) for merging and caution also are inconsistent among sites. These symbols are mostly experimental due to the lack of guidance for these symbols in the MUTCD. One exception is the Minnesota MUTCD, which provides additional guidance specific to the state of Minnesota and has long included guidance for use of the yellow arrow, as this symbol has been used on signage for a tunnel on I-94 for many years. Figure 3. Dynamic speed limit signs in Maine, left, and Oregon, right (FHWA, Oregon DOT). Multipurpose Overhead Lane Use Control Sign Deployments Corridors in urban areas of several states currently have electronic signs over each lane on a series of gantries to support ATM strategies, and are under construction in three additional states (i.e., Illinois, Michigan, and Nevada), as presented in Table 1. Following the table are additional details and examples of multipurpose lane use control sign deployments. These deployments are generally similar in terms of the information displayed to drivers: • Support display of regulatory or advisory dynamic speed limits, queue warning, and dynamic managed lane operations, including shoulder lane usage and restricted bus, high- occupancy vehicle (HOV), and high-occupancy toll (HOT) lanes for improved mobility by reducing crashes and managing recurring and non-recurring congestion. • Commonly a similar smaller-sized, full-color, dynamic sign, with capabilities to display various lane control symbols, as well as regulatory or advisory dynamic speed limits. • Green arrow and red X symbols are commonly used, consistent with MUTCD guidance. • Generally, default to blank for free-flow conditions. • Gantries are often spaced about a half-mile apart. These types of deployments are not always consistent in the types of information or how it is presented to drivers, including: • Different lane control symbols are used. A downward yellow arrow is sometimes used to denote “caution,” and diagonal arrows or a sequencing chevron are sometimes used for “merge” situations. Text is sometimes added above these symbols to facilitate driver understanding for “Merge,” “Closed,” or “Caution.” • ATM signs are sometimes presented on gantries with other static, regulatory signage.

11 • Larger DMS are often on the gantries to display an additional text message, however, the size and position of DMS on the gantry vary, as well as the spacing. The supplemental DMS may be a full-size DMS in the center or right side of the gantry, or a medium-sized DMS on one or both sides of the roadway, for example. A corridor may have supplemental DMS on every other gantry, for instance, or may have a mix of full-size DMS on some gantries and two medium-sized DMS on other gantries. • The display of regulatory or advisory dynamic speed limits can vary, as described in the Dynamic Speed Limit Deployments section. • The distance for providing advanced warning of a closed lane can vary by location. Deployments in Minnesota and Washington initially provided advance warning of a mile or more, but have since shortened this distance. The following examples and photos of deployments highlight some of the different ways that overhead lane use signage presents information to drivers. Special attention is paid to the provision of supplemental DMS, including the number, size, and position, as well as particular features in the corridor, such as managed lanes. California. Features of the Caltrans lane use control system on I-80 in the San Francisco Bay Area include: • Gantries have two supplemental medium-sized DMS at the same level as the lane control signs mounted on the sides for the display of advisory dynamic speeds, as shown in Figure 4; it is more common at other sites to display speed information on the signage over the lanes. • In addition, a supplemental full-sized DMS is mounted on the right side of some gantries for the provision of messages. • Gantries do not include other static signage.

12 Table 1. Overhead dynamic lane control signage deployments and accompanying strategies in the United States. La ne C on tr ol Sp ee d Li m it Sh ou ld er L an e Q ue ue W ar ni ng O th er S tr at eg y State & Route System Details x x x x CA: I-80 The SMART corridor in the San Francisco Bay Area provides lane control symbols, DMS for queue warning, and advisory dynamic speeds, as well as dynamic alternate routing on arterials. x x x CO: US 36, I-25 South Systems support queue warning, dynamic lane control, and advisory dynamic speeds. A HOT lane is on each corridor. x x DE: I-295 Deployed on the Delaware Memorial Bridge as part of Advanced Traffic Management System. x MA: I-93 Lane control signage in Boston that can display only X and down arrow graphics. x x x x x MN: I-35W, I-94 Systems provide queue warnings and formerly displayed dynamic advisory speeds in Minneapolis. A short dynamic shoulder segment on I-35W extends a HOT lane to a major interchange but will be retired following a highway reconstruction project. Dynamic junction control is used on a large dynamic message sign on I-94. x x x x x VA: I-66 Hard shoulder running for general purpose traffic during peak periods in peak directions began in 1992 on 7 miles of I-66 in Northern Virginia. Dynamic lane control, queue warning and dynamic speed limits installed in 2015 for all lanes on a longer segment allowed the dynamic shoulder lane segment to be based on real-time conditions. Entire system to be removed in 2017 due to a highway widening reconstruction project. x x x x WA: I-90, I-5 North, SR 520 Systems post dynamic speed limits and provide queue warning to drivers in Seattle. The signs can also quickly close entire lanes and caution drivers approaching an on-ramp with heavy merging traffic. Static signs with dynamic numbers provide travel times for alternate routes. x* x x* x OR: SR 217 Signs are used only for advisory speeds. Supplemental DMS provide travel time and incident information. *Software was pre-programmed with lane use control capabilities for future use, as necessary. x x x x IL: I-90 Under construction: will operate dynamic speed limits, dynamic lane control including a transit-only Flex Lane, and queue warning northwest of Chicago; managed by Illinois Tollway. x x x x MI: US 23 Under construction: will include a dynamic flex lane on the left shoulder, real-time queue warning, and possibly dynamic advisory speeds in Ann Arbor. x x x NV: I-15, I-515, US 95, US 93 Under construction: As part of Project NEON, a major construction project at the I-15 interchange with US 95, US 93, and I-515 in Las Vegas, a series of extra-large DMS are being installed to seamlessly span all lanes on those corridors to help manage traffic by displaying dynamic speed limits and lane control symbols. x TX: US 290 Discontinued: Signs in Austin are still in place but have not been used for years.

13 Figure 4. Lane use control signage on I-80 in the Bay Area (Caltrans). Colorado. Features of the Colorado DOT lane use control systems on I-25 south and US 36 in the Denver area include: • Gantries on corridors in Denver have a mix of providing zero, one, or two medium-sized DMS on the side(s) of the gantry at differing levels relative to the signs over the lane, as shown in Figure 5 and Figure 6. • Some gantries include a large DMS above the lane control signs, and these gantries may also have medium-sized DMS, as shown in Figure 6. • Some of these gantries also include static guide signs and static signage with dynamic elements that support HOT lanes on US 36 and a part of I-25 as shown in Figure 5. Figure 5. Lane use control signage on US 36 in Denver (Google Maps).

14 Figure 6. Lane use control signage on I-25 southbound in Denver (Google Maps). Delaware. Features of the Delaware Memorial Bridge lane use control systems on I-295 include: • Some gantries include static guide signs or full-size DMS. • Approximately every third gantry includes a two-part digital dynamic speed limit display in the middle, as seen in Figure 7. • Only a downward green arrow and X symbols can be displayed, as seen in Figure 7. Figure 7. Lane use control signage on the I-295 Delaware Memorial Bridge (Google Maps).

15 Illinois. The Illinois Tollway has erected gantries on the I-90 Jane Addams Tollway, as depicted in Figure 8 for lane use control operations that are expected to begin in 2017. The slightly larger lane control sign on the left will manage a dynamic shoulder “flex lane” for transit use only. Figure 8. Lane use control signage on the I-90 Tollway northwest of Chicago (Daily Herald). Massachusetts. Features of the Massachusetts DOT lane use control systems on I-93 in Boston include: • Some gantries include both static guide signs and full-sized supplemental DMS, as shown in Figure 9. • Lane control signs are only capable of displaying a downward arrow and X. Figure 9. Lane use control signage on I-93 in Boston (Google Maps). Minnesota. Features of the Minnesota DOT lane use control systems on I-35W and I-94 in the Minneapolis-St. Paul area include: • Gantries with lane control signage also contain static regulatory signage. • The deployment on I-35W also facilitates management of a HOT lane, which includes a dynamic shoulder lane segment, as seen in Figure 10. • The advisory dynamic speed shown in Figure 10 was not found to be effective and is no longer in use. • A three-stage sequencing chevron is used with “merge” text, which mimics an arrow board display used for work zones, as seen in Figure 11.

16 • Gantries do not generally include supplemental DMS. Figure 10. Lane use control signage on I-35W in Minneapolis (Google Maps). Figure 11. Lane use control signage on I-94 in Minneapolis (FHWA). Texas. Lane control signage on US 290 in Austin remains in place but is no longer used, as shown in Figure 12. Signs are capable of displaying only the downward arrow and X symbols. Figure 12. Lane use control signage on US 290 in Austin (Google Maps). Virginia. Features of the Virginia DOT lane use control system on I-66 in Northern Virginia include:

17 • Gantries have a supplemental full-sized DMS at the same level as the lane control signs mounted on either the left or right side for the provision of messages, as shown in Figure 13 and Figure 14. • One HOV lane operates in each direction of the entire ATM corridor. • Signage on a segment from US 50 to the I-495 Capital Beltway support dynamic shoulder lane operations, as seen in Figure 13. • When the shoulder is closed, a red X is displayed over that lane, as seen in Figure 13, except at on-ramps where a diagonal yellow arrow is displayed under the text “merge.” • Gantries do not include other static signage, as seen in Figure 13 and Figure 14. • Additional gantries with a single lane control sign are provided at intermediate distances as necessary to help support dynamic shoulder operations. • Route symbols have been used as a dynamic junction control application in at least one location to help designate a lane exclusively for exiting traffic. Figure 13. Lane use control signage on I-66 in Northern Virginia (Virginia DOT). Figure 14. Lane use control signage on I-66 in Northern Virginia (Virginia DOT).

18 Washington. Features of the Washington State DOT lane use control systems on I-5 northbound, I-90, and SR 520 in Seattle include: • A downward yellow arrow with “caution” text is used in the outside lane in advance of on-ramps with heavy traffic, as shown in Figure 15. • Dynamic speed limits for the HOV lane may be up to 15 miles per hour higher or lower than general purpose lanes, depending on real-time traffic conditions, as shown in Figure 15. • A diagonal arrow (or arrows) is used with accompanying “merge” text, as shown in Figure 16. • A white diamond for the HOV lane is sometimes made smaller to include text, e.g., “2+ only” or “open to all,” as shown in Figure 16. • Gantries on corridors in Seattle have a mix of providing one or two medium-sized DMS on the side(s) of the gantry at a slightly lower level than the signs over the lane, as shown in Figure 15, based on the number of lanes on the highway; one large DMS on the right side of the gantry, as shown in Figure 16; or no supplemental DMS in some locations. Figure 15. Lane use control signage on I-5 in Seattle (Google Maps). Figure 16. Lane use control signage on I-5 in Seattle (WSDOT).

19 Dynamic Lane Control and Dynamic Lane Reversal Lane control deployments exist in many locations to serve both arterial and freeway applications of lane reversal. However, most of these deployments operate on a static time-of-day basis, rather than dynamic, real-time congestion conditions. Many of these deployments are found in bridges, tunnels, or managed lanes. Lane reversal on arterials is typically controlled with overhead lane control signs that use either a downward green arrow or red X to convey whether the lane is opened or closed. Additional dynamic signs may be used in advance of intersections to demarcate appropriate turning movements, as seen in Figure 17 and Figure 18. Static signs may support operations by presenting the hours that the reversible lane is open to traffic for the given direction. Figure 17. Arterial lane control signs on 5400 South in Salt Lake City, Utah (Salt Lake City Tribune). Figure 18. Arterial lane control signs in Montgomery County, Maryland (Montgomery County DOT). Lane reversal on freeways often exists in barrier-separated managed lanes, either as a HOV lane or HOT lane. Given this context, signage for drivers is typically provided in advance of entry points to these lanes to convey whether the lane is opened or closed and, if applicable, the cost, as seen in Figure 19 and Figure 20. Additionally, a moveable barrier or gates are generally present at the entry point to control access.

20 Figure 19. Lane reversal deployment on I-595 HOT Lanes in Miami (Sun Sentinel). Figure 20. Lane reversal deployment on I-5 HOV Lanes in Seattle (Google Maps). Alternatively, lane reversal on freeways may incorporate a moveable barrier system that can shift the barrier during peak traffic flows, which reduces or eliminates the need for signage. This approach has also been used in a work zone application in Minnesota. Dynamic Shoulder Lane Deployments As described above in the Multipurpose Overhead Lane Use Control Sign Deployments section, dynamic shoulder lanes are sometimes deployed in conjunction with other ATM strategies in urban areas. Currently, dynamic shoulder lane operations exist in five states, and will soon open in Michigan, as shown in Table 2. However, due to highway widening projects, dynamic shoulder lane operations in three locations will be ending within a year. Additional details on these deployments are provided below. Colorado. Dynamic shoulder lane use in Colorado is unique as it is a rural deployment. However, eastbound I-70 sometimes experiences high traffic volumes, particularly on Sundays in winter months due to travelers returning to Denver from skiing. The striping and full-size, overhead DMS displaying the red X and text indicating the lane can currently be used for emergency stopping only is visible in Figure 21. Figure 21. Dynamic shoulder lane on I-70 East in Colorado (Google Maps).

21 Table 2. Current and planned dynamic shoulder lane deployments in the United States. State & Route System Details CO: I-70 East The 13-mile dynamically priced I-70 Mountain Express Peak Period Shoulder Lane near Idaho Springs opened in 2015 and operates only in peak periods. GA: I-85, SR 400 Dynamic Flex Shoulder Lanes include automatically controlled LED signs above the lane to indicate open/closed status in Atlanta. MN: I-35W North Ending soon: A 2-mile segment on I-35W in Minneapolis opened in 2009 to extend a managed lane to a major interchange but will be retired in 2018 due to a highway widening reconstruction project. Dynamic lane control and dynamic queue warning is also present for all lanes, and advisory speeds were previously posted. NJ: I-78 Ending soon: Dynamic shoulder lanes on a segment of the I-78 New Jersey Turnpike in Newark is permitted at static times of day temporarily during a construction project on a parallel route. Dynamic speed limits are also present. VA: I-66 Ending soon: Hard shoulder running for general purpose traffic during peak periods in peak directions began in 1992 on a 7-mile segment of I-66 between US 50 and I-495 in Northern Virginia. ATM signs began operations in September 2015 to allow dynamic shoulder lane use on this segment based on real-time conditions but will be retired in 2017 due to a highway widening reconstruction project. Dynamic lane control, queue warning and dynamic speed limits are also present for all lanes. VA: I-495 North This 1.5-mile segment opened in 2015 to allow traffic to travel on the left shoulder of northbound I-495 from where the 495 Express Lanes end to the George Washington Parkway in Northern Virginia. MI: US 23 Under construction: A dynamic flex lane on the left shoulder near Ann Arbor will be managed by a new system with signs over each lane that will provide real-time queue warning and possibly dynamic advisory speeds. Georgia. Near Atlanta, dynamic shoulder lanes called Flex Lanes operate on SR 400 and a one- mile segment of I-85 north. The overhead dynamic lane control signage and explanatory roadside static signage that is used on I-85 north is visible in Figure 22. The middle section of the static sign contains a diagonal yellow arrow pointing up and to the right, which had initially been proposed to communicate to drivers to “merge” when the lane was closing. Figure 22. Dynamic shoulder lane on I-85 North near Atlanta (Google Maps). Minnesota. The dynamic shoulder lane on the two-mile segment of I-35W north is deployed in conjunction with the larger lane use control signage as presented above, using the same symbols, lane control signs, and managed lane signage. The dynamic shoulder lane deployment on I-35W

22 was initially installed with in-pavement lighting at the beginning of the segment, as seen in Figure 23; however this was subsequently removed due to recurring maintenance issues. Dynamic shoulder lane usage will be suspended on this segment following a highway widening project that will begin in 2018. Figure 23. Dynamic shoulder lane on I-35W North in Minneapolis (Minnesota DOT). New Jersey. During a construction project on a parallel route, the New Jersey Turnpike deployed lane control signs to temporarily allow a dynamic shoulder lane on I-78 in Newark, as seen in Figure 24. Figure 24. Dynamic shoulder lane on the I-78 New Jersey Turnpike in Newark (FHWA). Virginia. Dynamic shoulder lanes on the seven-mile segment of I-66 are currently deployed in conjunction with the larger lane use control signage as presented above, using the same symbols, lane control signs, and managed lane signage. Additional gantries with a single lane control sign supplement the larger gantries to specifically support dynamic shoulder lane operations where needed, as shown in Figure 25. Figure 25 also shows how Virginia DOT is experimenting with

23 using the merge text and symbol at on-ramp locations when the dynamic shoulder is closed, instead of using the red X. This segment had previously operated as a static time of day shoulder since 1992, using static and dynamic signage, as well as the colored pavement depicted in Figure 26. Installation of the overhead lane use control gantries for all lanes in 2015 also enabled dynamic shoulder lane operations on the segment, such that the lane is open to traffic almost twice as much as before, as warranted by real-time traffic conditions, including off-peak periods and weekends. Figure 25. Dynamic shoulder lane on I-66 in Northern Virginia (Google Maps). Figure 26. Previous static time of day shoulder lane on I-66 in Northern Virginia (FHWA). Additionally, in 2015 the Virginia DOT opened a 1.5-mile shoulder section for static time-of-day usage during peak periods downstream of the I-495 Express Lanes on the Capital Beltway in Northern Virginia, as shown in Figure 27.

24 Figure 27. Dynamic shoulder lane on I-495 North in Northern Virginia (Google Maps). Dynamic Speed Limit Deployments Deployments of dynamic speed limits, also known as VSLs are widespread across the United States, as presented in Table 3. Dynamic speed limit deployments are used in a variety of applications to improve safety as well as mobility in both urban areas for recurring and non- recurring congestion, as presented in Table 4, and in rural areas for weather and work zone applications, as presented in Table 5 and Table 6, respectively. Table 3 presents a list of the locations and routes of dynamic speed limit deployments in the United States, including those discussed above as a part of Multipurpose Overhead Lane Use Control Sign Deployments. Variations presented in this table include whether the deployment is: • A regulatory speed limit that can be enforced or an advisory speed. • Primarily deployed to help with urban congestion, weather issues, work zone management, or other purposes like downhill safe speeds for trucks. • Signage is placed on the roadside or overhead. • Signage is fully dynamic or is a static sign that has a cutout for the display of dynamic numeral digits. • Used on signage that is also used for other ATM strategies. Table 4, Table 5, and Table 6 present photos of the dynamic speed limit signs used in most of the current deployments in the United States, to help visualize the differences in how drivers receive the information. Specifically: • Advisory speeds are presented in a variety of ways, e.g., the provision of text to say, “reduce speed” or “advisory speed,” or not. • Regulatory dynamic speed limits generally conform to MUTCD specifications of black and white signage, however static signs with black text on a white background may have dynamic numerals that are either white on a black background or vice versa. • Some deployments include flashing beacons to attract driver attention when a reduced speed is displayed. • The dynamic displays fall on a spectrum, employing flip discs, older technology lights, or full-color LED displays.

25 One additional item to note is the variations in how states provide information to drivers via supplemental DMS or dynamic elements on the dynamic speed limit signs to provide explanation for the reduced speed. For example, as depicted below in Table 5, an Oregon deployment on I-84 and a Washington deployment on I-90 at Snoqualmie Pass display a speed limit sign graphic on the left side of a full-size DMS and can provides text on the right side, e.g., “low visibility.” Similarly, dynamic speed limit signs in Tennessee on I-75 includes a dynamic element that displays “fog.” Supplemental medium- or full-sized DMS located in advance of or on the same gantry as dynamic speed limit signs can also provide explanation to drivers to justify and encourage travel at reduced speeds.

26 Table 3. Current, planned, and discontinued dynamic speed limit deployments in the United States. State and Route(s) Type Purpose Sign Location Sign Type W ith si gn s f or o th er A TM st ra te gi es System Location and Other Details R eg ul at or y A dv iso ry C on ge st io n W ea th er W or k Zo ne O th er R oa ds id e O ve rh ea d Fu lly D yn am ic D yn am ic D ig its AL: I-10 x x x x Low visibility warning system with flashing beacons. Near Mobile. CA: I-80 x x x x x In San Francisco Bay Area. CO: US 36, I-25 x x x x x In Denver. CO: I-70 x x x x Downhill truck speed warning system. Displays safe speed for each truck >40,000 lbs. gross vehicle weight based on its axle configuration, gross vehicle weight, and the downgrade of the highway incline. In Eisenhower Tunnel. DE: I-295 x x x x x Older signage technology, not fully digital. On Delaware Memorial Bridge. DE: I-495 x x x x In Wilmington. FL: I-4, US 27 x x x x In Orlando and Fort Lauderdale. GA: I-285 x x x x In Atlanta. IA: I-35 x x x x Test project. For winter weather. Displayed on portable DMS. KS x x x x Eight portable dynamic speed limit trailers were retained. MD x x x x Eight portable dynamic speed limit trailers. ME: I-95, I-295 x x x x Sign says, “maximum speed,” but is black text on yellow. In Portland. MI: I-96 x x x x Test project. Portable orange trailer with flashing beacon. In Lansing. MN: I-35, I-494 x x x x Test project. Used on two work zone projects on I-35 and I-494. MO: US 54, US 63 x x x x Near Columbia. NH: I-93 x x x x Near Concord. NJ: I-95, I-78 x x x x Dynamic digits are flip segment/disks at this site. Near Newark. NV: I-80, US 395 Alt x x Near Reno. OH: US 33, I-270 x x x x Includes flashing beacon. Speeds reduce based only on workers being present, not congestion. Other routes have used dynamic speed zones in work zones.