Accelerating Roundabout Implementation

in the United States – Volume VII of VII

Human Factor Assessment of Traffic Control

Device Effectiveness

PUBLICATION NO. FHWA-SA-15-075 SEPTEMBER 2015

Updated July 2020
https://www.fhwa.dot.gov/publications/convtabl.cfm
 

 

 

 

 

 

 

 

 

 

 

 

 

 

FOREWARD 

Since the Federal Highway Administration (FHWA) published the first Roundabouts 

Informational Guide in 2000, the estimated number of roundabouts in the United States has 

grown from fewer than one hundred to several thousand. Roundabouts remain a high priority for 

FHWA due to their proven ability to reduce severe crashes by an average of 80 percent. They 

are featured as one of the Office of Safety Proven Safety Countermeasures and were included in 

the Every Day Counts 2 campaign for Intersection & Interchange Geometrics. 

As roundabouts became more common across a wide range of traffic conditions, specific 

questions emerged on how to further tailor certain aspects of their design to better meet the needs 

of a growing number and diversity of stakeholders. The substantial work performed for this 

project – Accelerating Roundabout Implementation in the United States – sought to address 

several of the most pressing issues of national significance, including enhancing safety, 

improving operational efficiency, considering environmental effects, accommodating freight 

movement and providing pedestrian accessibility. This work represents yet another notable step 

forward in advancing roundabouts in the United States. 

The electronic versions of each of the seven report volumes that document this project are 

available on the Office of Safety website at http://safety.fhwa.dot.gov/. 

Michael S. Griffith 

Director 

Office of Safety Technologies 

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. This report does not constitute a standard, 

specification, or regulation. 

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. 

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TECHNICAL REPORT DOCUMENTATION PAGE 

1. Report No. 

FHWA-SA-15-075 

2. Government Accession No. 3. Recipient’s Catalog No. 

4. Title and Subtitle 

Accelerating Roundabout Implementation in the United States 

Volume 7: Human Factor Assessment of Traffic Control Device 

Effectiveness 

5. Report Date 

September 2015 

6. Performing Organization Code: 

7. Author(s) 

Daniel Findley1, Sarah Searcy1, Katy Salamati1, Bastian 

Schroeder1

, Brian Williams2, Rajaram Bhagavathula2, and Lee A. 

Rodegerdts3 

8. Performing Organization Report No. 

11861 Task 9 

9. Performing Organization Name and Address

1

Highway Systems Institute for Transportation Research and 

Education North Carolina State University, Raleigh, NC 27695;

2

Virginia Tech Transportation Institute, Blacksburg VA 24061;

3

Kittelson & Associates, Inc., Portland, OR 97205 

10. Work Unit No. 

11. Contract or Grant No. 

DTFH61-10-D-00023-T-11002 

12. Sponsoring Agency Name and Address 

Office of Safety 

Federal Highway Administration 

1200 New Jersey Avenue, SE 

Washington, DC 20590 

13. Type of Report and Period Covered 

Technical Report 

August 2011 through September 2015 

14. Sponsoring Agency Code 

FHWA HSA 

15. Supplementary Notes 

The Contracting Officer’s Technical Manager (COTM) was Jeffrey Shaw, HSST Safety Design Team 

16. Abstract 

This volume is seventh in a series of seven. The other volumes in the series are: Volume I - Evaluation of Rectangular 

Rapid-Flashing Beacons (RRFB) at Multilane Roundabouts, Volume II – Assessment of Roundabout Capacity Models for 

the Highway Capacity Manual, Volume III – Assessment of the Environmental Characteristics of Roundabouts, Volume IV 

– A Review of Fatal and Severe Injury Crashes at Roundabouts, Volume V – Evaluation of Geometric Parameters that 

Affect Truck Maneuvering and Stability, and Volume VI – Investigation of Crosswalk Design and Driver Behaviors. These 

reports document a Federal Highway Administration (FHWA) project to investigate and evaluate several important aspects 

of roundabout design and operation for the purpose of providing practitioners with better information, leading to more 

widespread and routine implementation of higher quality roundabouts. 

This report examined the relationship between signing and marking of multilane roundabouts and the likelihood of erratic 

maneuvers, and thus conflicts and crashes. The report documents two different studies: (1) observation of erratic maneuvers 

and conflicts from overhead video recordings; and (2) an in-vehicle eye tracker study to investigate driver gaze patterns and 

gaze direction while traversing multilane roundabouts. The two most dominant contributing factors to erratic maneuvers 

appear to be (1) inconsistencies between lane use markings on the approach and those within the circulatory roadway, and 

(2) insufficient channelization for drivers when being shifted from the inside lane to the outside lane to exit. Drivers also 

were more likely to glance at markings than at signs. 

17. Key Words 

Roundabout, traffic control devices, signing, pavement 

marking 

18. Distribution Statement 

No restrictions. This document is available to the public at 

http://safety.fhwa.dot.gov/ 

19. Security Classif. (of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of Pages 

97 

22. Price 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 

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TABLE OF CONTENTS 

FOREWARD.................................................................................................................................. i 

NOTICE.......................................................................................................................................... i 

QUALITY ASSURANCE STATEMENT ................................................................................... i 

TECHNICAL REPORT DOCUMENTATION PAGE............................................................. ii 

TABLE OF CONTENTS ............................................................................................................ iii 

LIST OF FIGURES ...................................................................................................................... v 

LIST OF TABLES..................................................................................................................... viii 

CHAPTER 1. INTRODUCTION............................................................................................... 1 

OBJECTIVE ............................................................................................................................. 1 

LITERATURE REVIEW ........................................................................................................ 1 

EXPERIMENTAL APPROACH ............................................................................................ 2 

CHAPTER 2. METHODOLOGY: VIDEO-BASED ERRATIC MANEUVER STUDY ..... 3 

DATA SET................................................................................................................................. 3 

TYPES OF ERRATIC MANEUVERS................................................................................... 5 

TYPES OF SIGNING AND PAVEMENT MARKINGS...................................................... 6 

DATA ANALYSIS.................................................................................................................... 6 

Pavement Marking and Erratic Maneuvers....................................................................... 7 

Lane Control Signing and Pavement Marking .................................................................. 7 

Volume and Percentage of Erratic Maneuvers .................................................................. 7 

CHAPTER 3. METHODOLOGY OF THE EYE-TRACKING STUDY............................... 9 

INDEPENDENT VARIABLES............................................................................................... 9 

Objects of Interest................................................................................................................. 9 

Marking and Sign Type...................................................................................................... 10 

Roundabout Location ......................................................................................................... 10 

DEPENDENT VARIABLES ................................................................................................. 11 

PARTICIPANTS .................................................................................................................... 11 

EQUIPMENT.......................................................................................................................... 11 

LOCATIONS .......................................................................................................................... 13 

EXPERIMENTAL PROCEDURE ....................................................................................... 13 

DATA REDUCTION.............................................................................................................. 13 

Glances................................................................................................................................. 13 

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Locations.............................................................................................................................. 14 

Number of Vehicles............................................................................................................. 15 

CHAPTER 4. RESULTS........................................................................................................... 17 

ERRATIC MANEUVERS VS. PAVEMENT LANE MARKINGS................................... 20 

ERRATIC MANEUVERS VS. TRAFFIC VOLUME ........................................................ 21 

EYE-GLANCE BEHAVIOR VS. OBJECT OF INTEREST ............................................. 23 

Percent of Glances and Dwell Time .................................................................................. 23 

Duration of Dwell and Fixation Times.............................................................................. 24 

EYE-GLANCE BEHAVIOR VS. MARKING AND SIGN TYPE..................................... 25 

EYE GLANCE BEHAVIOR VS. VEHICLE LOCATION................................................ 27 

EYE-GLANCE BEHAVIOR VS. ROUNDABOUT LOCATION ..................................... 28 

EYE-GLANCE BEHAVIOR VS. NUMBER OF VEHICLES........................................... 30 

DISCUSSION OF EYE GLANCE RESULTS..................................................................... 33 

CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS .......................................... 35 

RECOMMENDATIONS FOR FUTURE RESEARCH ..................................................... 36 

APPENDIX A. DETAILED SITE INVENTORY AND VIDEO-BASED CONFLICT 

STUDY......................................................................................................................................... 37 

APPENDIX B. EYE TRACKER STUDY POST-DRIVE QUESTIONNAIRE................... 69 

APPENDIX C. EYE TRACKER STUDY QUESTIONNAIRE RESULTS......................... 71 

APPENDIX D. EYE-TRACKER STUDY MANEUVERS (HILLIARD, OH).................... 77 

APPENDIX E. EYE-TRACKER STUDY MANEUVERS (CARMEL, IN) ........................ 83 

REFERENCES............................................................................................................................ 87 

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LIST OF FIGURES 

Figure 1. Photo. ViewPoint eye tracker goggles. ...................................................................... 12 

Figure 4. Diagram. Segmentation of the roundabouts for tracking vehicle and object 

Figure 5. Graph. Traffic volume vs. percentage of erratic maneuvers observed on the 

Figure 6. Graph. Traffic volume vs. percentage of erratic maneuvers observed in the 

Figure 7. Graph. Traffic volume vs. percentage of erratic maneuvers observed on the 

Figure 15. Charts. Comparison of total glances by object of interest between Carmel, IN 

Figure 16. Chart. Percentage of total glances by marking and sign type and roundabout 

Figure 17. Graph. Percent of glances by roundabout location and number of vehicles in the 

Figure 2. Screenshot. ViewPoint eye tracker software............................................................ 12 

Figure 3. Diagram. Example segment for eye glance data collection and analysis............... 14 

locations. ...................................................................................................................................... 15 

approach and in the circle.......................................................................................................... 21 

circulatory roadway (all Hilliard roundabouts)....................................................................... 22 

approach (all Hilliard roundabouts). ........................................................................................ 22 

Figure 8. Pie Chart. Percentage of the total number of glances by object of interest. ......... 23 

Figure 9. Pie Chart. Percentage of the total dwell time by object of interest........................ 24 

Figure 10. Graph. Mean dwell time by object of interest. ....................................................... 25 

Figure 11. Graph. Mean fixation time by object of interest.................................................... 25 

Figure 12. Chart. Total glances and mean dwell time by marking and sign type. ............... 26 

Figure 13. Chart. Percent of total glances by marking and sign type and vehicle location. 27 

Figure 14. Chart. Mean dwell time by marking and sign type and vehicle location ............ 28 

and Hilliard, OH. ........................................................................................................................ 29 

location. ........................................................................................................................................ 30 

roundabout. ................................................................................................................................. 31 

Figure 18. Graph. Mean dwell time by object of interest and roundabout location. ........... 32 

Figure 19. Graph. Mean fixation time by object of interest and roundabout location. ....... 33 

Figure 20. Photo. Avon Rd./Benchmark Rd., Avon, CO......................................................... 38 

Figure 21. Photo. Avon Rd./Beaver Creek Blvd., Avon, CO .................................................. 39 

Figure 22. Photo. Avon Rd./US 6, Avon, CO............................................................................ 41 

Figure 23. Photo. Edwards Access Rd./Beard Creek Rd./I-70 WB Ramps, Edwards, CO . 42 

Figure 24. Photo. Edwards Access Rd./I-70 EB Ramps, Edwards, CO................................. 43 

Figure 25. Photo. Edwards Access Rd./Miller Ranch Rd., Edwards, CO ............................. 44 

Figure 26. Photo. S. Golden Rd./Johnson St./16th Ave., Golden, CO.................................... 45 

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Figure 27. Photo. Hazel Dell Pkwy./126th St., Carmel, IN ..................................................... 47 

Figure 45. Chart. Questionnaire results for “How many years have you been driving in the 

Figure 46. Chart. Questionnaire results for “Do you drive through a single-lane or a multiFigure 47. Chart. Questionnaire results for “How many times a week do you drive through 

Figure 48. Chart. Questionnaire results for “I am comfortable negotiating traffic and 

Figure 49. Chart. Questionnaire results for “I am comfortable navigating through 

Figure 50. Chart. Questionnaire results for “I am comfortable negotiating and choosing my 

Figure 51. Chart. Questionnaire results for “I am comfortable negotiating and choosing my 

Figure 28. Photo. Illinois St./116th St., Carmel, IN ................................................................. 49 

Figure 29. Photo. SR 67/Blacksmith Dr./Kelch Dr., Malta, NY ............................................. 50 

Figure 30. Photo. SR 67/I-87 SB Ramps, Malta, NY ............................................................... 52 

Figure 31. Photo. SR 67/I-87 NB Ramps, Malta, NY............................................................... 53 

Figure 32. Photo. SR 67/US 9, Malta, NY................................................................................. 54 

Figure 33. Photo. SR 67/State Farm Blvd., Malta, NY............................................................ 55 

Figure 34. Photo. 14th Ave./Jefferson St., Olympia, WA........................................................ 56 

Figure 35. Photo. 4th Ave./Olympic Way, Olympia, WA ....................................................... 57 

Figure 36. Photo. Borgen Blvd./51st Ave. NW, Gig Harbor, WA .......................................... 58 

Figure 37. Photo. Harbor Hill Dr./Development Entrance, Gig Harbor, WA...................... 59 

Figure 38. Photo. SR 539/Pole Rd., Lynden (Whatcom County), WA................................... 60 

Figure 39. Photo. SR 539/Ten Mile Rd., Lynden (Whatcom County), WA .......................... 61 

Figure 40. Photo. SR 539/Wiser Lake Rd., Lynden (Whatcom County), WA...................... 62 

Figure 41. Photo. Jackson St./Murdock Ave., Oshkosh, WI................................................... 63 

Figure 42. Photo. Main St./Cemetery Rd., Hilliard, OH......................................................... 64 

Figure 43. Photo. Main St./Scioto Darby Rd., Hilliard, OH ................................................... 66 

Figure 44. Chart. Questionnaire results for “How many hours a day do you drive?” ........ 71 

United States?”............................................................................................................................ 71 

lane roundabout?” ...................................................................................................................... 72 

a roundabout (or multiple roundabouts)?”.............................................................................. 72 

choosing my lane at the entry of a roundabout.” ..................................................................... 73 

roundabouts.”.............................................................................................................................. 73 

lane at the exit of a roundabout.”.............................................................................................. 74 

lane in the circulating lanes of a roundabout.” ........................................................................ 74 

Figure 52. Chart. Questionnaire results for “Pavement markings help me navigate as I 

approach and drive through a roundabout.”........................................................................... 75 

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Figure 53. Chart. Questionnaire results for “Signs help me as I approach and drive 

through a roundabout.” ............................................................................................................. 75 

Figure 54. Chart. Questionnaire results for “Which of the following do you pay more 

Figure 57. Diagrams. Hilliard OH roundabout - Main St., Cemetery Rd., and Scioto Darby 

Figure 62. Diagrams. Carmel, IN roundabout – Old Meridian St. and N. Pennsylvania St. 

attention to as you approach and drive through the roundabouts?”..................................... 76 

Figure 55. Diagrams. Hilliard OH roundabout - Main St. and Scioto Darby St. ................. 77 

Figure 56. Diagrams. Hilliard OH roundabout - Main St. and Cemetery Rd. ..................... 78 

Rd. ................................................................................................................................................ 79 

Figure 58. Diagrams. Hilliard, OH roundabout - Leap Rd. and Anson Dr. ......................... 80 

Figure 59. Diagrams. Hilliard, OH roundabout – Britton Pkwy and Anson Dr................... 80 

Figure 60. Diagram. Hilliard, OH roundabout – Britton Pkwy and Davidson Rd............... 81 

Figure 61. Diagrams. Carmel, IN roundabout – Old Meridian St. and Grand Blvd. .......... 83 

....................................................................................................................................................... 84 

Figure 63. Carmel, IN roundabout – Clay Terrace Blvd, North Roundabout. ..................... 84 

Figure 64. Carmel, IN roundabout – Clay Terrace Blvd, South Roundabout. ..................... 85 

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LIST OF TABLES 

Table 1. Sites for video-based erratic maneuvers study............................................................ 4 

Table 2. Categories of erratic maneuvers................................................................................... 6 

Table 3. Roundabout signs and pavement marking types. ....................................................... 6 

Table 5. Objects of interest. ....................................................................................................... 10 

Table 6. Eye-tracking study dependent variables.................................................................... 11 

Table 7. Roundabout Approach and Circulatory Roadway Erratic Maneuvers ................. 18 

Table 8. Observed Volumes and Erratic Maneuvers at Avon Rd./Benchmark Rd., Avon, 

CO................................................................................................................................................. 38 

Table 9. Observed Volumes and Erratic Maneuvers at Avon Rd./Beaver Creek Blvd., Avon, 

CO................................................................................................................................................. 39 

Table 10. Observed Volumes and Erratic Maneuvers at Avon Rd./US 6, Avon, CO

Table 11. Observed Volumes and Erratic Maneuvers at Edwards Access Rd./Beard Creek 

........... 41 

Rd./I-70 WB Ramps, Edwards, CO .......................................................................................... 42 

Table 12. Observed Volumes and Erratic Maneuvers at Edwards Access Rd. /I-70 EB 

Ramps, Edwards, CO ................................................................................................................. 43 

Table 13. Observed Volumes and Erratic Maneuvers at Edwards Access Rd./Miller Ranch 

Rd., Edwards, CO ....................................................................................................................... 44 

Table 14. Observed Volumes and Erratic Maneuvers at S. Golden Rd./Johnson St./16th 

Ave., Golden, CO ........................................................................................................................ 45 

Table 15. Observed Volumes and Erratic Maneuvers at Hazel Dell Pkwy./126th St., Carmel, 

IN .................................................................................................................................................. 47 

Table 16. Observed Volumes and Erratic Maneuvers at Illinois St./116th St., Carmel, IN . 49 

Table 17. Observed Volumes and Erratic Maneuvers at SR 67/Blacksmith Dr./Kelch Dr., 

Malta, NY..................................................................................................................................... 50 

Table 18. Observed Volumes and Erratic Maneuvers at SR 67/I-87 SB Ramps, Malta,NY52 

Table 19. Observed Volumes and Erratic Maneuvers at SR 67/I-87 NB Ramps, Malta, NY 

....................................................................................................................................................... 53 

Table 20. Observed Volumes and Erratic Maneuvers at SR 67/US 9, Malta, NY................ 54 

Table 21. Observed Volumes and Erratic Maneuvers at SR 67/State Farm Blvd., Malta, NY 

....................................................................................................................................................... 55 

Table 22. Observed Volumes and Erratic Maneuvers at 14th Ave./Jefferson St., Olympia, 

WA................................................................................................................................................ 56 

Table 23. Observed Volumes and Erratic Maneuvers at 4th Ave./Olympic Way, Olympia, 

WA................................................................................................................................................ 57 

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Table 24. Observed Volumes and Erratic Maneuvers at Borgen Blvd./51st Ave. NW, Gig 

Harbor, WA................................................................................................................................. 58 

Table 25. Observed Volumes and Erratic Maneuvers at Harbor Hill Dr./Development 

Entrance, Gig Harbor, WA........................................................................................................ 59 

Table 26. Observed Volumes and Erratic Maneuvers at SR 539/Pole Rd., Lynden 

(Whatcom County), WA............................................................................................................. 60 

Table 27. Observed Volumes and Erratic Maneuvers at SR 539/Ten Mile Rd. , Lynden 

(Whatcom County), WA............................................................................................................. 61 

Table 28. Observed Volumes and Erratic Maneuvers at SR 539/Wiser Lake Rd., Lynden, 

(Whatcom County) WA.............................................................................................................. 62 

Table 29. Observed Volumes and Erratic Maneuvers at Jackson St./Murdock Ave., 

Oshkosh, WI ................................................................................................................................ 63 

Table 30. Observed Volumes and Erratic Maneuvers at Main St./Cemetery Rd., Hilliard, 

OH ................................................................................................................................................ 65 

Table 31. Observed Volumes and Erratic Maneuvers at Main St./Scioto Darby Rd., 

Hilliard, OH................................................................................................................................. 67 

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CHAPTER 1. INTRODUCTION 

Prior research has shown roundabouts to have lower rates of severe and fatal crashes than 

signalized intersections and two-way stop-controlled intersections (Rodegerdts et al. 2007). 

However, isolated serious-injury and fatal crashes have occurred at roundabouts, as reported in 

Volume 4, Review of Fatal and Severe Injury Crashes at Roundabouts. Some multilane 

roundabouts have also been reported to have an unusually high occurrence of property damageonly crashes (Richfield et al. 2014, Bill et al. 2011). A possible explanation for these crashes, 

explored in this study, is that they may be attributable to traffic control devices such as signing 

and marking. Even though the severity of crashes at roundabouts may lower than that at traffic 

signals, the tendency for a high frequency of low-severity crashes to occur at some multilane 

roundabouts is an issue that warrants attention as roundabouts become more common. 

OBJECTIVE 

The objective of this research was to develop insights into the relationship between signing and 

marking of multilane roundabouts and the likelihood of erratic maneuvers that may lead to 

conflicts and crashes. To evaluate the performance of multilane roundabouts with respect to 

erratic maneuvers, the team performed two different studies: (1) observation of erratic 

maneuvers and conflicts from overhead video recordings; and (2) an in-vehicle eye tracker study 

to investigate driver gaze patterns and gaze direction while traversing multilane roundabouts. 

The two studies complemented each other in that, conceptually, the observation of erratic 

maneuvers and conflicts was a macroscopic study of a broad sample of vehicles across many 

sites, and the in-vehicle eye-tracker study was a pseudo-naturalistic study of driver eye 

movements at a subset of sites. 

LITERATURE REVIEW 

The majority of studies conducted on signs and pavement markings at roundabouts in the United 

States precede the Federal Highway Administration’s 2009 Manual on Uniform Traffic Control 

Devices (MUTCD) (Hanscom 2009, Molino et al. 2007, Inman et al. 2006) and are based 

primarily on driver simulator experiments involving various sign types. 

Few studies have used field-based measurements of before-and-after safety performance related 

to choices of signs and pavement markings. One of the few instances documented in the 

literature is at a site in Richfield, MN, where a two-lane roundabout replaced a signalized 

intersection in 2008. After the conversion, the roundabout experienced an unexpected number of 

property damage only (PDO) crashes. The city sought to identify potential contributory factors 

for the crashes as well as low cost solutions to the PDO crash problem. Signing and striping 

changes that were made included replacing fishhook arrows with standard arrows (with a dot to 

represent the central island), adding turn arrows and lane designation signs approximately 450 

feet upstream of the yield line on all legs, extending the solid line from 50 feet to 250 feet 

upstream of the yield line, changing circulating lane striping to a 3-foot stripe/1-foot gap pattern 

with a 6-inch-wide stripe, lowering the mounting height of some signs, and increasing the size of 

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the YIELD signs. Richfield et al. (2014) conducted an observational study at that roundabout 

using overhead video before and after the signing and striping changes were made between 2010 

and 2011. They studied yield violations, lane change violations, turn violations, incorrect lane 

choice, wrong way movements, and stopping events. Results showed that, after the signing and 

striping changes, yielding violations decreased by 25 percent, turning violations decreased by 55 

percent, and incorrect lane choice decreased by 59 percent. All reductions were significant at the 

95 percent confidence level except for yield violations. These results were attributed to a 

combination of application of guidelines from the 2009 MUTCD and options for circulatory 

roadway striping taken from the National Cooperative Highway Research Program (NCHRP) 

Report 672, each intended to reinforce to drivers the importance of choosing the correct lane 

prior to entry. However, because all signing and striping changes were made at the same time, it 

is not possible to isolate the effects of individual changes. 

From this literature review, it becomes evident that there is a gap in evaluating actual driver 

behavior in the field at different roundabouts, which may lead to a better grasp of actual conflict 

patterns and driver gaze patterns while traversing a roundabout. This research was therefore 

field-based in order to better understand actual driver behaviors as they relate to roundabout 

signing and marking. 

EXPERIMENTAL APPROACH 

Based on the current state of roundabout signing and marking practices, several key research 

questions were identified and used to develop the underlying research hypothesis, which 

informed this project’s methodology, experimental design, and site selection. Two different 

methodologies were applied in this project: a video-based erratic-maneuver study of roundabouts, 

and an eye-tracker study of drivers in roundabouts. The video-based erratic maneuver study was 

a comprehensive study to identify the proportion of drivers making erratic maneuvers or causing 

vehicle-to-vehicle conflicts while driving through the roundabouts. The rate of these proxy safety 

events was then evaluated relative to the marking and signing at the studied two-lane 

roundabouts. The purpose of this study was to articulate targeted research questions for the eye 

tracker study. The eye tracker study was then intended to provide a more in-depth analysis of 

drivers’ gaze patterns as they travel through a roundabout, and to identify what signs and 

markings drivers pay more attention to. The following sections describe the two experiments’ 

methodologies in detail. 

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CHAPTER 2. METHODOLOGY: VIDEO-BASED ERRATIC MANEUVER STUDY 

The first study in this task was a video-based study of vehicle erratic maneuvers and conflicts. 

The goal of the study was to understand patterns of conflicts and erratic maneuvers, and relate 

those to signing and marking at the studied roundabouts. Therefore, a data set containing video 

of roundabouts was identified. Erratic maneuvers were defined and categorized, as were types of 

signing and pavement markings. Data analysis consisted of reducing video data and identifying 

correlations between erratic maneuvers and signing and pavement markings, and is described in 

this section. 

DATA SET 

The team utilized available video of multilane roundabouts from prior research efforts, including 

NCHRP Project 03-65 (Roundabouts in the United States), NCHRP Project 03-100 (Evaluating 

the Performance of Corridors with Roundabouts), and video recorded for the research described 

in Volume 1 and Volume 2 of this broader FHWA research effort. The team inventoried the 

available video for data that could be used for this effort. Overall, the conflict study identified 

164 hours of usable overhead video from 40 multilane roundabout legs in 10 U.S. cities, as listed 

in Table 1. Each leg is categorized by compass direction; a south leg, for example, is equivalent 

to a northbound approach. 

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1 

2

3

4

5 

6

7

8

9

10

11 

12 

13 

14 

15 

16 

17 

18 

19

20

21

22

23

24

25

26

27

28

29

30

Table 1. Sites for video-based erratic maneuvers study. 

No. ID City State Intersection Leg 

Avon-1 Avon CO Avon Rd./Beaver Creek 

Blvd. South 

Avon-2 Avon CO Avon Rd./Benchmark Rd. North 

Avon-3 Avon CO Avon Rd./US 6 West 

Avon-4 Avon CO Avon Rd./US 6 North 

Avon-5 Avon CO Avon Rd./Beaver Creek 

Blvd. East 

Avon-6 Avon CO Avon Rd./Benchmark Rd. South 

Carmel-1 Carmel IN Illinois St./116th St. East 

Carmel-2 Carmel IN Illinois St./116th St. South 

Carmel-3 Carmel IN Hazel Dell Pkwy./126th St. East 

Carmel-4 Carmel IN Hazel Dell Pkwy./126th St. North 

Edwards-1 Edwards CO Beard Creek Rd./I-70 WB 

Ramps North 

Edwards-2 Edwards CO Beard Creek Rd./I-70 WB 

Ramps East 

Edwards-3 Edwards CO Edwards Access Rd./Miller 

Ranch Rd. East 

Edwards-4 Edwards CO Edwards Access Rd./I-70 

EB Ramps West 

Edwards-5 Edwards CO Edwards Access Rd./Miller 

Ranch Rd. South 

Gig Harbor-1 Gig Harbor WA Harbor Hill 

Dr./Development Entrance North 

Gig Harbor-2 Gig Harbor WA Borgen Blvd./51st Ave. 

NW East 

Golden-1 Golden CO S. Golden Rd./Johnson 

St./16th Ave. Southeast 

Lynden-1 Lynden WA SR 539/Pole Rd. North 

Lynden-2 Lynden WA SR 539/Wiser Lake Rd. North 

Lynden-3 Lynden WA SR 539/Pole Rd. South 

Lynden-4 Lynden WA SR 539/Ten Mile Rd. South 

Malta-01 Malta NY SR 67/US 9 West 

Malta-02 Malta NY SR 67/I-87 SB Ramps East 

Malta-03 Malta NY SR 67/I-87 SB Ramps West 

Malta-04 Malta NY SR 67/I-87 NB Ramps West 

Malta-05 Malta NY SR 67/I-87 NB Ramps East 

Malta-06 Malta NY SR 67/US 9 East 

Malta-07 Malta NY SR 67/State Farm Blvd. East 

Malta-08 Malta NY SR 67 /State Farm Blvd. West 

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No. ID City State Intersection Leg 

31 Malta-09 Malta NY SR 67/Kelch Dr. West 

32 Malta-10 Malta NY SR 67/Kelch Dr. East 

33 Olympia-1 Olympia WA 4th Ave./Olympic Way South 

34 Olympia-2 Olympia WA 14th Ave./Jefferson St. North 

35 Olympia-3 Olympia WA 4th Ave./Olympic Way East 

36 Olympia-4 Olympia WA 14th Ave./Jefferson St. South 

37 Oshkosh-1 Oshkosh WI Jackson St./Murdock Ave. West 

38 Oshkosh-2 Oshkosh WI Jackson St./Murdock Ave. East 

39 Hilliard-1 Hilliard OH Main St./Cemetery Rd. West 

40 Hilliard-2 Hilliard OH Main St./Scioto Darby Rd. Southeast 

Following the video inventory, a trained analyst watched the video and identified erratic 

maneuvers and conflicts. To keep the data reduction consistent, only one person conducted the 

video data reduction for the entire erratic-maneuver study. 

TYPES OF ERRATIC MANEUVERS 

For this study, erratic maneuvers were defined as any improper or illegal movement at the 

roundabout that did not impact other traffic. A conflict was defined as the subset of erratic 

maneuvers resulting in a near crash between two or more vehicles, and instances where vehicles 

needed to take evasive actions, such as rapid braking or lane changing, to avoid a crash. Due to a 

very low frequency of observed conflicts, conflicts were combined with erratic maneuvers to 

increase sample size. In addition, in most cases, due to camera view, it was not possible to 

separate conflicts from other erratic maneuvers. No crashes were observed within the video 

reviewed for this study. 

The team identified the following five types of erratic maneuvers of particular interest for this 

study that drivers could perform when driving through a multilane roundabout. They are listed 

and described in Table 2. Other erratic maneuvers that can occur at multilane roundabouts, 

including wrong way maneuvers on the approach, wrong way maneuvers within the circulatory 

roadway, failure to yield on approach, and yielding within the circulatory roadway, were found 

to be infrequent and outside the scope of this study. Observations of these other erratic 

maneuvers are documented in Appendix A, but are not discussed further in this report. Only 

passenger cars were observed for erratic maneuvers for this study. 

5 
 

 

 

Table 2. Categories of erratic maneuvers. 

Position Erratic Maneuver 

Name Description 

Approach Lane change Driver enters the wrong lane of the circulatory 

roadway from the roundabout entry 

Approach Improper turn Driver uses the left lane to make a right turn 

Circulatory 

Roadway Lane change Driver changes lane within circulatory roadway 

Circulatory 

Roadway Improper turn 

Driver exits from inside lane of circulatory 

roadway when not allowed by pavement 

markings 

Circulatory 

Roadway Lane straddle Driver drives on lane lines 

TYPES OF SIGNING AND PAVEMENT MARKINGS 

For each observed roundabout, the team collected an inventory of signs and markings at 

roundabout entry approaches and circulatory lanes using available photos in Google Street View. 

Nine types of signs and three types of pavement markings were included in the study, as listed in 

Table 3. The table includes designations from the 2009 MUTCD as appropriate, although in 

some cases the signs at individual sites were not compliant with the 2009 MUTCD. This study 

did not look at the effect of variations within a single sign type (e.g., variations of the W2-6 

Circular Intersection Sign). 

Table 3. Roundabout signs and pavement marking types. 

Type Name 

Sign Circular Intersection Sign (W2-6) 

Sign Advance Lane Control Sign (R3-8) 

Sign Destination Sign (e.g., D1-1d) 

Sign Roundabout Directional Arrow (R6-4) 

Sign One Way Sign (R6-1) 

Sign Yield Ahead Sign (W3-2) 

Sign Yield Sign (R1-2) 

Pavement marking Lane Striping 

Pavement marking Lane Use Marking (normal arrows or fish-hook arrows) 

Pavement marking Yield Line 

DATA ANALYSIS 

The data reductionist observed approximately one hour of video for each site, with the exception 

of the two Hilliard sites, for which 13 hours of video were available for each site and were 

analyzed separately. In each case, the approach volume, circulatory roadway volume, and 

frequency of erratic maneuvers were normalized into hourly rates over the observed time period. 

6 
 

 

 

 

 

 

 

 

 

 

 

 

 

For each of the roundabout approaches, the flow rate of vehicles entering the roundabout 

(approach volume in vehicles per hour, calculated as a rate over the period of observation) and 

the flow rate of circulating vehicles passing in front of the entry (circle volume in vehicles per 

hour, calculated as a rate over the period of observation) were counted. In addition, the number 

of vehicles causing any of the erratic maneuvers was recorded. From those counts, the 

percentage of erratic maneuvers for each type of erratic maneuver was calculated by dividing the 

number of vehicles causing that particular type of erratic maneuver by the volume observed. 

Pavement Marking and Erratic Maneuvers 

The goal of the analysis regarding erratic maneuvers and lane marking was not to provide a 

comprehensive safety audit of each location, but rather to provide a high-level identification of 

trends related to pavement markings that can be generalized to design practice. 

Available multilane roundabout video was screened to identify locations with erratic maneuvers 

as described in this study. At those sites, the team focused on the layout of pavement markings 

such as lane-use arrows, lane striping, and channelization striping, and attempted to identify 

trends regarding pavement markings and erratic maneuvers. Pavement markings were observed 

using aerial photos available from Google Earth, and the details of each site review are provided 

in Appendix A. Dates of the aerial photos were variable but were generally from 2012 (the year 

of the majority of the video used for this study) or as near to it as possible; dates are indicated in 

Appendix A. 

Lane Control Signing and Pavement Marking 

The team created an inventory of the existence, location, and count of lane-control signs and 

lane-use pavement markings at each of the roundabout approaches to see whether the count and 

type (markings versus signing) would have an effect on erratic maneuvers. The study sites were 

categorized by number of sets of lane-control signs and lane-use markings on the roundabout 

approach. The team then tallied the rate of erratic maneuvers for each lane-control designation. 

Volume and Percentage of Erratic Maneuvers 

The team examined whether there was a relationship between the number of erratic maneuvers 

observed and the average observed flow rate on the approach and circulatory roadway. 

7 

 

 

 

 

 

 

 

 

 

CHAPTER 3. METHODOLOGY OF THE EYE-TRACKING STUDY 

The eye-tracking experiment was a pseudo-naturalistic study in which participants drove on a 

test route through several roundabouts while wearing an eye tracker. The study is described as 

pseudo-naturalistic because the environment and interactions with other vehicles and pedestrians 

were as they would have occurred naturally, but the experimenter determined the route that the 

participants drove. The route was designed to include particular intersections and maneuvers, but 

all other interactions with vehicles, pedestrians, and the environment along the route were 

naturalistic. 

INDEPENDENT VARIABLES 

Data for several independent variables were collected by the eye-tracking equipment and are 

listed and described in Table 4. In a true naturalistic study, many different independent variables 

can be selected based on the question the researcher intends to answer, and are limited only by 

what data was collected. For this experiment, the research team wanted to determine what drivers 

glanced at, where they glanced, and from which part of the roundabout they made these glances. 

Therefore, the following variables were defined and pulled from the eye-tracker data. 

Table 4. Eye-tracking study independent variables. 

Variable Description (values) 

Objects of Interest 

The object category at which the drivers’ eyes were directed 

(traffic, pedestrians, signs, markings, pedestrian-related signs and 

markings) 

Marking and Sign Type Per table 3 

Vehicle Location Location of vehicle at time of gaze (approach, entrance, circle, exit) 

Number of Vehicles Estimated number of vehicles in the roundabout at the time a glance 

occurred 

Objects of Interest 

One research goal was to determine the objects at which participant drivers gazed while 

traversing the roundabouts. Objects of interest were grouped into five main categories: traffic, 

pedestrians, markings, signs, and pedestrian-related markings and signs. Crosswalks and 

pedestrian crossing signs were put into this last category because their purpose is not to assist in 

navigating the roundabouts, but to alert drivers to possible pedestrian encounters, so they form a 

separate semantic class. The items in each object of interest category are listed in Table 5. 

9 
 

 

 

 

 

 

 

 

 

Table 5. Objects of interest. 

Category Object of Interest 

Traffic Vehicles in or near the roundabout 

Pedestrians Pedestrians in or near the roundabout 

Markings Lane Striping (circulatory roadway) 

Markings Lane Use Marking (circulatory roadway and 

approach) 

Markings Yield Line 

Signs Circular Intersection Sign (W2-6) 

Signs Destination Sign (e.g., D1-1d) 

Signs Roundabout Directional Arrow (R6-4) 

Signs Lane Control Sign (R3-8) 

Signs One Way Sign (R6-1) 

Signs Yield Ahead Sign (W3-2) 

Signs Yield Sign (R1-2) 

Pedestrian-related 

Signs and Markings Crosswalk Striping 

Pedestrian-related 

Signs and Markings 

Pedestrian Crossing & Yield to Pedestrian Signs 

(S1-1, W11-2, R1-6) 

Marking and Sign Type 

To analyze eye behavior with respect to marking and sign type, the categories of traffic, 

pedestrians, and pedestrian-related signs and markings were removed, and the category of 

markings and signs was divided into subcategories for marking and sign types. Those categories 

are listed in Table 3. 

To further differentiate between the types of lane marking in the roundabout, the lane striping 

within the circulatory roadway was divided into three categories: right (outer) edge line, center 

lane line, and left (inner) edge line. This was done because it was determined that participants 

used the different lane lines for different reasons. Most glances toward the right edge line 

marking occurred before the participant entered the roundabout, and this marking acted similarly 

to a yield line. However, when within the circulatory roadway, participants tended to glance 

toward the center lane line and left edge line for guidance and staying within their lane. 

Roundabout Location 

The roundabouts included in the eye-tracker study in Carmel, IN had less signage and fewer 

markings than those in Hilliard, OH. The roundabouts in Carmel, IN had pavement markings on 

approach and at the entrance to the circulatory roadway that showed indications of wear (i.e. they 

had not recently been reapplied). The roundabouts in Hilliard, OH had pavement markings that 

had been more recently applied and showed fewer indications of wear. Therefore, the research 

team examined the differences in eye glance behavior between the two locations. 

10 
 

 

 

 

 

 

 

 

 

DEPENDENT VARIABLES 

Data for several dependent variables were collected by the eye-tracking equipment, and are listed 

and described in Table 6. 

Table 6. Eye-tracking study dependent variables. 

Variable Description (values) 

Glance Count 

How many times participants looked at an object. A glance was defined as 

any instance in which the gaze point remained on a particular object for at 

least two video frames (~69 ms). 

Fixation Time 

The length of time between saccades. Saccades are rapid eye movements 

that quickly change the point of fixation. These can be voluntary, but also 

occur reflexively any time the eyes are open, even while fixating on a target. 

(Purves, 2001) 

Dwell Time 

The duration in milliseconds that a glance remained directed at a particular 

object. Dwell time is the sum of all saccades and fixation times that occurred 

while the gaze remained directed at a particular object. 

PARTICIPANTS 

Participants were recruited using flyers posted in each of the locations where testing occurred, as 

well as through word-of-mouth. A total of 21 participants completed the eye-tracking study. 

Participants ranged in age from 18 to 72 years old, with a median age of 39. Twelve males and 

nine females participated. Participants had to successfully complete a screening questionnaire 

over the phone to be eligible for participation. Participants had to be at least 18 years old, hold a 

valid driver’s license, and not have any medical conditions or taking any medications that might 

make it unsafe for them to drive. Participants were compensated $50. 

EQUIPMENT 

The study used a ViewPoint eye tracker, a head-mounted system that uses infrared lights and 

cameras mounted on a plastic frame to track the movement of the wearer’s eyes (Figure 1). The 

eye tracker also includes a forward-facing color camera to record the scene in front of the wearer. 

After calibration, the eye tracker provides a video recording of the scene with the wearer’s gaze 

point overlaid on the photo, as well as the XY coordinates of the gaze point and fixation times, 

among other variables. A screenshot is shown in Figure 2. 

The frames are connected to a laptop with a cable that runs behind the wearer’s right ear. This 

cable is clipped to the wearer’s shirt to prevent pulling on the frames, and allows unrestricted 

movement of the wearer’s head. The system calculates eye movement with an accuracy of 

between 0.25 and 1 degrees of visual arc, and a spatial resolution of approximately 0.15 degrees 

of visual arc. 

11 
Figure 1. Photo. ViewPoint eye tracker goggles. 

Figure 2. Screenshot. ViewPoint eye tracker software. 

12 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LOCATIONS 

The study was conducted in two locations: Carmel, IN and Hilliard, OH. These locations were 

selected for their high density of roundabouts. A total of nine different roundabouts were 

included in the study, four in Carmel, IN and five in Hilliard, OH. Eight were two-lane 

roundabouts, and one was a single-lane roundabout with one two-lane approach (designated as a 

through-left lane and a right-turn-only lane). Routes were designed so participants performed 21 

different movements through these roundabouts: 5 left turns, 3 right turns, 3 U-turns, and 10 

through movements (see Appendices E and F for experiment details). 

EXPERIMENTAL PROCEDURE 

Participants were instructed to meet the research team in a parking lot near the test route at their 

scheduled time. Upon arrival, participants were greeted by an experimenter who administered the 

informed-consent form, which they were asked to read and sign. 

After completing the paperwork, participants were escorted to the vehicle, familiarized with the 

vehicle controls (e.g., seat, mirror, and steering adjustments), and fitted with the eye-tracker, 

which was then calibrated. An experimenter explained the instructions for the study: that the 

experimenter would provide directions for the travel route, to refrain from casual conversation, 

and to drive safely. The participant was then instructed to begin the drive and directed along the 

test route. The participant was offered no guidance for lane selection, and only told which way to 

turn at an upcoming roundabout. 

Depending on traffic conditions, driving the test route took participants approximately 40 

minutes to 1 hour. Upon return to the starting point, participants filled out a post-drive 

questionnaire (See Appendix B for questionnaire and Appendix C for detailed results.) asking 

about their experience and comfort level with driving through roundabouts, and they were 

compensated and dismissed. The driving routes for Hilliard, OH, and Carmel, IN, are provided in 

Appendices D and E respectively. 

DATA REDUCTION 

Glances 

A ‘glance’ was defined as the duration of time that a participant’s gaze rested on an object of 

interest. A glance did not include any transitional movements from one glance to the next, unless 

the gaze simply moved from one part of an object to another (such as scanning one side of a 

crosswalk to the other). A glance would begin as soon as the gaze point stopped on an object, 

and end just before the gaze point moved away from the object. A glance also had to last for at 

least two video frames (~69 ms) to be included. Any glance that lasted less than two video 

frames was indistinguishable from transitional or random eye movements due to the limitations 

of the eye tracker. 

Data reductionists began analyzing glances for a particular roundabout when the participant was 

approximately 73.2 m (250 ft) upstream from the first roundabout-related sign or marking. A 

circular intersection sign (W2-6) indicating the presence of a downstream roundabout was 

usually the first sign on the approach. Data reductionists stopped analyzing glances for a 

13 
14 

roundabout once the participant vehicle reached the exit crosswalk. Figure 3 shows an example 

of these points. 

Figure 3. Diagram. Example segment for eye glance data collection and analysis. 

When data reductionists found glances to the objects of interest, they entered the times at which 

the glance began and ended into a spreadsheet. They also entered contextual information that 

existed at the beginning of the glance, such as which lane the participant was in, where in the 

roundabout they were located, etc. 

Locations 

To examine how drivers’ glance patterns changed as they drove through the roundabouts, each 

roundabout was conceptually divided into four areas (the approach, entrance, circle, and exit) as 

shown in the example in Figure 4. These areas were always based on the participant’s 

perspective, and not on cardinal direction. The entrance and exit areas included the crosswalk in 

that leg, and the area between the circle and the crosswalk. Additional location information was 

collected for glances at pedestrians (e.g., whether they were on sidewalk, crosswalk, or splitter 

island). 
15 

Figure 4. Diagram. Segmentation of the roundabouts for tracking vehicle and object locations. 

Number of Vehicles

Data reductionists estimated the number of vehicles present for each glance using the eye-tracker 

video. Any vehicle that was visible in the eye tracker video, and was within the circulatory 

roadway, or areas between the circulatory roadway and crosswalks, were counted.

 

 

 

CHAPTER 4. RESULTS 

This section presents results for the video-based erratic maneuver study, followed by the eyetracking study. Table 7 lists the roundabouts used for the video-based erratic maneuver study. 

The table includes roundabout location, approach, and average frequency of each type of these 

erratic maneuvers per entry, and circulating volume for the video hours observed. 

17 
Table 7. Roundabout Approach and Circulatory Roadway Erratic Maneuvers 

ID 

Approach 

Volume 

(vph) 

Approach 

Lane 

Change 

(percent) 

Approach 

Turn 

(percent) 

Circulatory 

Roadway 

Volume 

(vph) 

Circulatory 

Roadway 

Lane 

Straddle 

(percent) 

Circulatory 

Roadway 

Lane 

Change 

(percent) 

Circulatory 

Roadway 

Turn 

(percent) 

Avon-1 493 4.1 0.0 496 3.4 1.0 1.2 

Avon-2 627 4.0 0.0 342 10.2 0.0 1.0 

Avon-3 410 4.6 0.0 529 0.9 14.0 2.1 

Avon-4 667 2.2 0.0 311 14.8 5.8 0.0 

Avon-5 416 11.5 6.0 966 0.5 5.0 0.9 

Avon-6 557 5.4 0.0 327 1.5 12.5 2.1 

Carmel-1 849 0.6 0.1 231 10.5 6.1 0.0 

Carmel-2 1585 2.0 0.0 545 2.2 0.7 0.4 

Carmel-3 118 15.3 0.0 1344 0.1 0.0 0.1 

Carmel-4 127 5.5 0.0 800 0.1 4.8 0.0 

Edwards-1 692 2.6 0.0 224 1.8 0.0 0.0 

Edwards-2 217 0.9 0.0 417 0.0 0.0 0.2 

Edwards-3 172 1.7 3.5 592 0.0 1.5 0.3 

Edwards-4 657 0.8 0.0 397 2.5 3.0 0.3 

Edwards-5 245 9.0 0.0 791 3.0 4.9 0.0 

Gig Harbor-1 318 2.5 0.0 69 0.0 0.0 0.0 

Gig Harbor-2 1002 1.2 0.0 229 6.0 10.0 3.6 

Golden-1 543 0.0 0.0 334 2.1 1.8 12.9 

Lynden-1 632 0.6 0.2 144 0.0 0.0 2.1 

Lynden-2 613 1.0 0.0 160 0.0 0.0 0.0 

Lynden-3 808 1.0 0.0 26 0.0 0.0 0.0 

Lynden-4 688 0.0 0.1 47 0.0 0.0 4.3 

Malta-1 682 0.7 0.1 496 2.8 4.4 0.8 

18 
ID 

Approach 

Volume 

(vph) 

Approach 

Lane 

Change 

(percent) 

Approach 

Turn 

(percent) 

Circulatory 

Roadway 

Volume 

(vph) 

Circulatory 

Roadway 

Lane 

Straddle 

(percent) 

Circulatory 

Roadway 

Lane 

Change 

(percent) 

Circulatory 

Roadway 

Turn 

(percent) 

Malta-2 950 0.6 0.0 34 0.0 0.0 0.0 

Malta-3 393 2.3 0.0 389 7.0 8.2 0.0 

Malta-4 703 1.4 0.0 47 0.0 9.0 8.0 

Malta-5 350 2.9 0.0 859 5.0 8.0 0.0 

Malta-6 343 0.9 0.0 709 2.0 6.0 3.0 

Malta-7 682 2.1 0.0 73 0.0 0.0 0.0 

Malta-8 602 6.0 0.0 127 7.0 12.0 0.0 

Malta-9 541 1.5 0.0 53 6.4 11.0 7.5 

Malta-10 495 7.1 0.0 106 8.5 10.4 0.9 

Olympia-1 532 3.9 0.0 812 0.0 0.0 0.1 

Olympia-2 642 1.7 0.0 704 9.2 3.8 0.1 

Olympia-3 1078 1.0 0.1 538 0.0 4.5 0.4 

Olympia-4 209 1.0 0.0 718 0.0 0.0 0.0 

Oshkosh-1 602 0.0 0.0 729 0.0 2.4 0.2 

Oshkosh-2 448 1.8 0.0 593 3.0 8.2 0.0 

Mean 571 2.9 0.3 429 2.9 4.2 1.4 

50th Percentile 580 1.8 0.0 393 1.7 3.4 0.2 

75th Percentile 682 4.0 0.0 676 4.6 7.5 1.2 

90th Percentile 879 6.3 0.1 804 8.7 10.6 3.8 

19 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ERRATIC MANEUVERS VS. PAVEMENT LANE MARKINGS 

The team reviewed the lane markings at sites with high rates (rates in the 75th percentile or 

higher among sites studied) of the following maneuvers: approach lane change, circulating lane 

change, circulating turn, and circulating lane straddle. The research team identified three major 

observations in the relationship between pavement markings and erratic maneuvers, which are 

discussed here. 

First, the large number of erratic maneuvers in the circulatory roadway (circulating lane change, 

circulating turn, and circulating lane straddle) at some sites can most likely be attributed to 

inconsistencies between the lane-use marking at the approach and that in the circulatory roadway. 

For some roundabouts, no indication was provided that a left lane of a two-lane approach was a 

left-turn only lane. In some cases the lack of left-turn-only designation appears to be because 

there were no lane use markings. In other cases, the lack of left-lane-only designation appears to 

be because the roundabout approach has a through arrow incorrectly in the left lane. Presumably, 

this is because designers were concerned drivers would misinterpret the left-lane indication 

arrows and go the wrong way in the roundabout. If the left lane were incorrectly marked as a 

through lane, drivers starting in the left lane and intending to go through the roundabout must 

make a lane change, turn, or straddle to exit. These erratic maneuvers can likely be minimized by 

using lane-use signing and marking throughout the entire roundabout consistent with the 

guidance in the MUTCD. This study observed no wrong-way maneuvers in the circulatory 

roadway, so the concern that proper lane marking leads to wrong-way turns may be unwarranted. 

Second, at a number of sites, circulating lane straddle and circulating lane change maneuvers 

appear to be correlated with the presence of inadequate channelization (through spiraling) to shift 

drivers from the inside lane to the outside lane for some left-turn maneuvers. This spiraling is 

illustrated in the MUTCD in a number of figures, including figures 3C-4 and 3C-5. Several 

roundabouts with an abnormally high proportion of these erratic maneuvers had very short 

spirals, often no more than one or two vehicle lengths. Some drivers followed the alignment of 

the edge of the truck apron rather than the stripes, resulting in abrupt lane shifts when exiting. 

Although further analysis was not conducted as part of this research, it may be possible to 

minimize these erratic maneuvers by using longer and smoother spirals to minimize the amount 

of change in curvature drivers encounter. In addition, although it could not be confirmed through 

this study, using physical channelization may also prove more effective, especially during 

inclement weather when markings could be obscured by rain or snow. Possible avenues to 

explore include extending the truck apron to form the spiraling rather than using spiraling 

pavement markings alone, and using the channelization techniques associated with the turboroundabout design technique being used in the Netherlands and elsewhere. 

Finally, some of the circulating lane straddle maneuvers could be attributed to the alignment of 

lanes between the entry and circulatory roadway. This path alignment is discussed at length in 

Section 6.5.4 of NCHRP Report 672. Some lane straddles were observed when the drivers were 

not in the immediate presence of other vehicles, allowing the driver to assume a path similar to a 

‘fastest path’ alignment through the circulatory roadway. It is unknown whether the same drivers 

would stay in their lane in the presence of other drivers, thus making this particular trend appear 

less consequential than the trends discussed previously. 

20 
 

 

 

 

 

 

 

 

ERRATIC MANEUVERS VS. TRAFFIC VOLUME 

The team examined whether there was a relationship between the number of erratic maneuvers 

and the average observed flow rate on the approach and circulatory roadway. Figure 5 shows the 

percent of total approach erratic maneuvers by approach volume and the percent of total circle 

erratic maneuvers by circle volume. In general, as the traffic volume increased, the percent of 

erratic maneuvers decreased. However, since the R2 is very low in both cases (0.04 and 0.16, 

respectively), no relationship can be concluded across the wide variation in geometries presented 

in the full data set. 

Volume vs. Percent Erratic Maneuvers (EMs) 

Percent Erratic Maneuvers 

20.0% 

18.0% 

16.0% 

14.0% 

12.0% 

10.0% 

8.0% 

6.0% 

4.0% 

2.0% 

0.0% 

0 200 400 600 800 1000 1200 1400 1600 1800 

R2 = 0.0358 

R2 = 0.1622 

Volume (vph) 

Approach Volume vs. Total Approach EMs Circulating Volume vs. Total Circulating EMs 

Linear (Approach Volume vs. Total Approach EMs) Linear (Circulating Volume vs. Total Circulating EMs) 

Figure 5. Graph. Traffic volume vs. percentage of erratic maneuvers observed on the 

approach and in the circle. 

The team conducted a more focused examination at the two Hilliard roundabouts where more 

time periods of data were available and where the differences in geometry and driver population 

across all study sites could be narrowed. Figure 6 shows the percent of total circulatory roadway 

erratic maneuvers by circulatory roadway volume, and Figure 7 shows the percent of approach 

erratic maneuvers by approach volume. In both cases, no relationship can be seen with the 

percentage of circulating lane straddles versus circulating volume or approach lane straddles 

versus approach volume. However, circulatory roadway lane changes decrease with an increase 

in circulating volume with a reasonably strong negative exponential trend (R2

 of 0.58), and 

approach roadway lane changes also decrease to a lesser extent with an increase in approach 

volume also decrease to a lesser extent (R2 of 0.16). This suggests that as volumes increase, 

particularly in the circulatory roadway, drivers appear to be paying more attention to proper lane 

selection for completing their desired turning movements. 

21 
 

 

 

R2 = 0.0013 

R2 = 0.5751 

0.00% 

0.50% 

1.00% 

1.50% 

2.00% 

2.50% 

3.00% 

3.50% 

4.00% 

4.50% 

5.00% 

0 200 400 600 800 1000 1200 1400 

Percentage of Erratic Maneuvers 

Hourly Volume 

Traffic Volume and Percentage of Circulatory Roadway 

Erratic Maneuvers (All Hilliard Roundabouts) 

Lane Straddle Lane Change Linear (Lane Straddle) Expon. (Lane Change) 

Figure 6. Graph. Traffic volume vs. percentage of erratic maneuvers observed in the 

circulatory roadway (all Hilliard roundabouts). 

R2 = 0.164 

0.00% 

1.00% 

2.00% 

3.00% 

4.00% 

5.00% 

6.00% 

0 100 200 300 400 500 600 700 

Percentage of EMs 

Hourly Volume 

Traffic Volume and Percentage of Approach Erratic 

Maneuvers (All Hilliard Roundabouts) 

Lane Straddle Lane Change Linear (Lane Change) 

Figure 7. Graph. Traffic volume vs. percentage of erratic maneuvers observed on the 

approach (all Hilliard roundabouts). 

22 
 

 

 

 

 

 

EYE-GLANCE BEHAVIOR VS. OBJECT OF INTEREST 

Eye glance behavior was compared among the five categories of objects of interest: traffic, 

pedestrian, markings, signs, and pedestrian-related markings and signs. 

Percent of Glances and Dwell Time 

Figure 8 shows the total glance count and the total dwell time of glances for each category of 

object of interest, and Figure 9 shows the percentage of total dwell time by object of interest. Out 

of the 1,759 glances that were reduced (which added up to over 14 minutes of total dwell time), 

glances at traffic were most common, and accounted for over half of all the time participants 

spent glancing at objects of interest in the roundabouts. Pedestrian-related signs and markings 

accounted for over a quarter of all glances and nearly a quarter of all dwell time. Glances 

towards crosswalks accounted for most of these. Glances toward other markings and signs made 

up less than a third of all glances, and less than a quarter of all dwell time. Very few pedestrians 

were encountered during data collection, resulting in only 19 total glances at pedestrians. 

Pedestrian glances occurred in eight different instances among six different participants. 

Figure 8. Pie Chart. Percentage of the total number of glances by object of interest. 

23 
 

 

 

Figure 9. Pie Chart. Percentage of the total dwell time by object of interest. 

Duration of Dwell and Fixation Times 

Figure 10 shows the mean dwell time, and Figure 11 the mean fixation time, for each object of 

interest. Fixation time is the length of time between saccades, and dwell time is the total amount 

of time a participant’s gaze was focused on an object. A single dwell time can comprise several 

fixations. 

The mean dwell time for glances at pedestrians was far longer than that of any other object of 

interest. Glances toward pedestrians lasted more than 1 s on average, twice as long as glances 

toward other vehicles, and roughly three times as long as glances toward markings or signs. 

Additionally, pedestrian glances had a longer mean fixation time (89 ms) than any other object of 

interest. Mean fixation times for the remaining objects of interest were very similar; all fell 

within 7 ms of each other. 

24 
Figure 10. Graph. Mean dwell time by object of interest. 

Figure 11. Graph. Mean fixation time by object of interest. 

EYE-GLANCE BEHAVIOR VS. MARKING AND SIGN TYPE 

To make comparisons among the pavement markings and signs intended to help drivers navigate 

through roundabouts, the objects of interest of traffic, pedestrians, and pedestrian-related signs 

25 
 

 

 

 

 

and markings were removed from the analysis, and the remaining objects were categorized as 

described in table 3. 

This left a total of 493 glances. Figure 12 shows the total number of glances and the mean dwell 

time for each of the markings and sign types. The majority of glances were toward lane use 

markings in the circulatory roadway, and center lane striping in the circulatory roadway. 

Together, these two markings accounted for nearly 54% of glances to signs and markings. These 

two markings also appear directly in front of the participant’s vehicle, which may help explain 

the large number of glances toward them. 

Figure 12. Chart. Total glances and mean dwell time by marking and sign type. 

Yield-ahead signs had the lowest mean dwell time at 166 ms. This may suggest that these signs 

are easily recognized and understood. Lane control signs had the highest mean dwell time at 

575 ms. This may suggest drivers need a longer amount of time in order to interpret the 

information on the sign. By comparison, the mean dwell time for circulatory roadway lane use 

markings—the pavement marking equivalent of lane control signs—was 376 ms, 199 ms shorter 

than the mean dwell time for lane control signs. 

26 
 

 

 

 

 

 

 

 

 

 

EYE GLANCE BEHAVIOR VS. VEHICLE LOCATION 

Figure 13 shows the percentage of total glances toward the different marking and sign types by 

the vehicle’s location: the approach, entrance, or circle. Signs and markings, which accounted for 

less than 1% of glances are not shown. The entrance was defined as the area between the 

crosswalk and the circle, where drivers yield before entering the circle (section A2 in figure 4). 

During the approach, participants glanced toward the lane use markings in the circulatory 

roadway far more than any other sign or marking. While in the entrance, participants made many 

fewer glances at signs and markings in general compared to when they were in the approach or 

the circle. This is likely due to the fact that they were only in the entrance for a short time, and 

needed to spend that time looking for traffic. Of the glances that were made in the entrance, most 

were toward the lane striping in the circulatory roadway. While in the circle, participants glanced 

at the lane striping most often, followed next by the lane use markings. 

Figure 13. Chart. Percent of total glances by marking and sign type and vehicle location. 

Figure 14 shows the mean dwell time for each sign and marking type by the vehicle location. 

Marking and sign types with the highest percentage of glances are highlighted. Those with fewer 

than three total glances were excluded; as such a small sample likely does not accurately 

represent mean dwell times. While in the approach, glances toward lane control signs had the 

highest mean dwell time. While in the entrance, glances toward yield lines had a considerably 

27 
 

 

 

 

 

longer mean dwell time than those at other marking and sign types. Glances toward destination 

signs had the longest mean dwell time for drivers in the circle. 

Figure 14. Chart. Mean dwell time by marking and sign type and vehicle location 

EYE-GLANCE BEHAVIOR VS. ROUNDABOUT LOCATION 

Figure 15 shows the percentage of total glances for roundabouts by category of object of interest 

in Carmel, IN and Hilliard, OH. Drivers in Carmel, IN made a much higher percentage of 

glances toward traffic than those in Hilliard, OH, while Hilliard drivers made a higher percentage 

of glances toward markings, and pedestrian-related signs and markings. However, the 

roundabouts in Hilliard tended to have more markings and pedestrian-related signs, which likely 

explains this difference. For example, roundabouts in Hilliard often had lane use markings within 

the circulatory roadway, and some intersections had overhead pedestrian-crossing signs, whereas 

those in Carmel did not. The percentage of glances towards signs and pedestrians was roughly 

the same between the two roundabout locations. 

28 
 

 

Figure 15. Charts. Comparison of total glances by object of interest between Carmel, IN 

and Hilliard, OH. 

Figure 16 shows the percentage of glances by marking and sign type for the two locations 

(markings and sign types with less than 1% of glances are not shown). The 22% fewer glances 

that drivers in Hilliard, OH made toward traffic seem to be spread out among the next four mostglanced-at objects. Among crosswalks, circulatory-roadway lane use markings, circulatoryroadway lane striping, and yield-to-pedestrian signs, Hilliard, OH drivers made 23% more 

glances than drivers in Carmel, IN. 

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Figure 16. Chart. Percentage of total glances by marking and sign type and roundabout 

location. 

EYE-GLANCE BEHAVIOR VS. NUMBER OF VEHICLES 

Glances toward traffic comprised a larger percentage of glances in Carmel, IN, than in Hilliard, 

OH. That was not because there was more traffic in Carmel, IN; there was less traffic per glance 

in Carmel, IN than in Hilliard, OH. Carmel averaged 1.8 vehicles in the roundabout per glance, 

and Hilliard averaged 2.4. 

Figure 17 shows the percent of all glances for each roundabout location versus the number of 

vehicles in the roundabout at the time the glance occurred. Most glances that occurred in Carmel, 

IN, (about 30%) occurred when there were no other vehicles within the roundabout. Only about 

17% of glances that occurred in Hilliard, OH, occurred when there were no other vehicles in the 

roundabout. Glances that occurred when there were four or more other vehicles in the 

roundabout made up a larger percentage of glances that occurred in Hilliard, OH, than in Carmel, 

IN. These results suggest that traffic volume is not the only factor affecting number of glances 

towards traffic. 

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Figure 17. Graph. Percent of glances by roundabout location and number of vehicles in the 

roundabout. 

Drivers in the two roundabout locations share a trend with respect to the object of interest and 

mean dwell times (Figure 18). In both locations, pedestrians had the longest mean dwell times, 

and signs and markings the shortest mean dwell times. However, drivers in Carmel, IN had 

longer dwell times for every category of object of interest than those in Hilliard, OH. It is 

possible that the roundabouts in Hilliard, OH—particularly those along Main St.—had more 

visually complex scenes with more signs, markings, and traffic than those in Carmel, IN, which 

caused drivers in Hilliard, OH to frequently shift their gaze, reducing mean dwell times. 

31 
 

 

 

Figure 18. Graph. Mean dwell time by object of interest and roundabout location. 

A similar effect was found when comparing drivers’ mean fixation time between the cities, as 

shown in Figure 19Figure 19, where drivers in Carmel, IN tended to have longer mean fixation 

times than those in Hilliard, OH. One notable exception was mean fixation time for pedestrian 

glances, which was virtually identical between the two cities and had a difference of only 1.29 

ms. 

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Figure 19. Graph. Mean fixation time by object of interest and roundabout location. 

DISCUSSION OF EYE GLANCE RESULTS 

When considering the combined data from Carmel, IN and Hilliard, OH, it appears that drivers 

do not spend a great deal of time looking at roundabout-related signs or markings. Together, they 

accounted for only 28% of all glances tracked for this study, which only included glances toward 

a specific list of objects. When drivers do glance at markings and signs related to the 

roundabouts, they look at markings (350 glances) 2.7 times as much as at signs (131 glances). A 

similar pattern occurred for the pedestrian-related signs and markings. Drivers glanced at 

crosswalks a total of 360 times, and at yield-to-pedestrian/pedestrian-crossing signs 125 times. 

On average, drivers spent slightly less time glancing at markings (380 ms) than at signs (401 ms). 

However, this effect varied between the two roundabout locations. Drivers in Hilliard, OH had a 

slightly longer mean dwell time (30.3 ms longer) for markings than for signs, while drivers in 

Carmel, IN, had a slightly longer mean dwell time (13 ms longer) for signs than markings. When 

comparing glances on approach at lane control signs and lane use markings that present similar 

information to the driver, the difference in dwell times between markings and signs was more 

pronounced. When the vehicle was approaching the roundabout, glances at lane control signs 

lasted, on average, 575 ms, about 32% (140 ms) longer than the mean dwell time for glances at 

lane use markings on approach. Additionally, drivers glanced at lane use markings in the 

approach 123 times compared to just 30 glances at lane control signs in the approach. The larger 

number of glances made toward lane use markings in the approach may be partially because lane 

use markings are in the lane, where they largely overlap with a forward-looking driver’s gaze. 

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Although participant responses to the questionnaire indicated they feel signs and markings are 

both important for navigating through a roundabout (Appendix C), the eye glance data suggests 

that drivers are more likely to look for guidance from markings on the pavement than at signs, 

and that they require less time per glance to do so. This seems to be the case regardless of where 

the driver is in the roundabout. In the approach, drivers glanced most often at lane use markings 

to determine which lane they should be in. In the entrance, drivers glanced most often at the 

outer circulatory roadway lane striping to know where to stop before entering, and in the circle, 

drivers glanced most often at the center circulatory roadway lane striping for guidance through 

the roundabouts. However, this result might have been different if the roundabouts in Carmel, IN 

had lane use markings in the circulatory roadway like those in Hilliard, OH. 

One caveat to consider, however, is that all of the data collection for this study occurred during 

daylight hours and in clear weather. It is possible that a different pattern would emerge at night, 

when signs appear brighter in a driver’s headlamps, or when the pavement is wet and markings 

become more difficult to see. Additionally, data collection also occurred in two locations where 

there are a large number of roundabout intersections, and all participants indicated that they were 

comfortable driving through roundabouts (Appendix C). Drivers who are inexperienced with 

roundabouts may have different glance patterns. 

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CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS 

This research included a video-based erratic maneuver study to examine the effect of roundabout 

signing and marking on erratic maneuvers in a large sample of study locations, and an eyetracker study to examine drivers’ eye glance behavior in roundabouts. 

The video-based study found that some pavement marking applications appear to result in a 

greater likelihood of erratic maneuvers. The two most dominant contributing factors appear to be 

(1) inconsistencies between lane use markings on the approach and those within the circulatory 

roadway, and (2) insufficient channelization for drivers when being shifted from the inside lane 

to the outside lane to exit. Another contributing factor to erratic maneuvers, but of lesser 

consequence, appears to be a discrepancy in lane alignment from the entry lane to the receiving 

circulating lane. 

Both of these dominant contributing factors identified above are related in that they are products 

of lane configurations involving exclusive movements rather than default movements that would 

be in place without any special lane designations (e.g., left-turn-only versus shared left-through). 

It appears prudent to be judicious in the design process when identifying the need for exclusive 

lanes and to be cautious when relying on signing and striping alone to convey the intended paths 

for these movements. It also appears prudent to conduct post-construction field reviews for sites 

with these exclusive movements to determine whether erratic maneuvers are occurring and 

whether any field adjustments to the signing, striping, and/or geometry may be beneficial. This 

research did not look into the extent to which these erratic maneuvers are significantly different 

from what may be experienced at other intersection forms with similar exclusive lanes, so it is 

not possible on the basis of this research alone to conclude that the observed phenomena are 

unique to roundabouts or that techniques suggested here to address these issues may also be 

beneficial at other intersection forms. Further experimentation and research in this area is 

recommended. 

The eye tracker study showed that when navigating roundabouts during daylight hours and clear 

weather conditions, drivers were more likely to glance at markings than at signs. Specifically, 

drivers made approximately three times more glances toward markings than toward signs, 

suggesting that drivers rely more heavily on pavement markings than signs to navigate through 

roundabouts. When similar information is presented by a sign and a marking (i.e., lane control 

sign and lane use marking), drivers glance toward the marking more often, and spend less time 

per glance. The eye tracker study showed that, when the vehicle was approaching the roundabout, 

drivers glanced at lane use pavement markings four times as much as at lane control signs, and 

those glances were on average 140 ms shorter, suggesting potentially a more intuitive 

understanding. 

The overall conclusion that can be drawn from these two studies is that correct pavement 

markings appear to be the most important traffic control devices to minimize erratic maneuvers, 

and thus conflicts and crashes. Drivers appear to focus considerably more attention on the 

markings than on signs, thus making communication of lane use and correct alignment via 

pavement marking beneficial. The study does not suggest that pavement markings should replace 

signing, but it is important that roundabout approaches and the circulatory roadway be equipped 

35 
 

 

 

 

 

 

with at least some lane use pavement markings that are correct for the lane configuration of the 

intersection. As noted above, the video-based erratic maneuver study suggests that the absence or 

incorrect use of lane use pavement markings on the approach is one of the contributing factors to 

erratic maneuvers within the roundabout as drivers make last-minute lane changes. 

RECOMMENDATIONS FOR FUTURE RESEARCH 

In addition to the recommended research and experimentation associated with exclusive lanes as 

described above, a recommendation for future research is to conduct a targeted investigation on 

the effect of various marking patterns within the circulatory roadway (and no striping) on driver 

behavior. A particular focus should be a comparison of various spiraling patterns and physical 

extensions of the truck apron to determine their effectiveness with respect to vehicle path 

alignment through the roundabout. Since field studies are confounded by differences in driver 

culture and geometry as was evident in the video-based conflict study performed here, a beforeafter study at selected locations that can reproduce the physical variations in these spiraling 

patterns across a range of observed driver patterns may be the preferred research approach. 

36 
 

 

 

 

APPENDIX A. DETAILED SITE INVENTORY AND VIDEO-BASED CONFLICT 

STUDY 

This section presents an individual evaluation for each roundabout. Each of the erratic 

maneuvers logged are provided in a table for each roundabout for the studied legs. For the erratic 

maneuvers of interest in this study (approach lane change, approach turn, circulating straddle, 

circulating lane change, and circulating turn), the percentile rankings are provided if the 

particular value exceeds the 75th percentile among the sites studied (excluding the Hilliard sites, 

which were analyzed separately). 

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Table 8. Observed Volumes and Erratic Maneuvers at Avon Rd./Benchmark Rd., Avon, CO 

 

 

Avon Rd./Benchmark Rd., Avon, CO 

This roundabout, completed in 1997, is illustrated in figure 20. Observed volumes and erratic 

maneuvers are provided in table 8. 

Figure 20. Photo. Avon Rd./Benchmark Rd., Avon, CO (Source: Google Maps 2015) 

Observed Volume or Erratic Maneuver South Leg (Avon-6) North Leg (Avon-2) 

Approach volume (veh/h) 557 627 

Circulating volume (veh/h) 327 342 

Approach lane change (percent) 5.4 (84th percentile) 4.0 (76th percentile) 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 1.5 10.2 (95th percentile) 

Circulating lane change (percent) 12.5 (97th percentile) 0.0 

Circulating turn (percent) 2.1 1.0 

Circulating yield (percent) 0.3 0.0 

Both the north and south legs have a standard left-through, through-right lane configuration, 

although the left-turn arrow is omitted from the pavement markings in the left lane on the 

approach. However, lane changes and lane straddles within the circulatory roadway are likely 

caused by the circulatory roadway lane configuration, which designates the inside circulating 

lane as left-turn only (a trap lane). No spiral markings or physical channelization is provided to 

guide the northbound and southbound left-turn movements into the outside circulating lane to 

avoid this trap. In addition, the westbound left entry lane is designated as a through movement on 

the entry but is actually a left-turn only lane once inside the roundabout. These alignment and 

lane designation inconsistencies are the likely causes of the observed erratic maneuvers. 

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Table 9. Observed Volumes and Erratic Maneuvers at Avon Rd./Beaver Creek Blvd., Avon, CO 

 

 

 

 

Avon Rd./Beaver Creek Blvd., Avon, CO 

This roundabout, completed in 1997, is illustrated in figure 21. Observed volumes and erratic 

maneuvers are provided in table 9. 

Figure 21. Photo. Avon Rd./Beaver Creek Blvd., Avon, CO (Source: Google Maps 2015) 

Observed Volume or Erratic Maneuver South Leg (Avon-1) East Leg (Avon-5) 

Approach volume (veh/h) 493 416 

Circulating volume (veh/h) 496 966 

Approach lane change (percent) 4.1 (79th percentile) 11.5 (97th percentile) 

Approach turn (percent) 0.0 6.0 (100th percentile) 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 3.4 0.5 

Circulating lane change (percent) 1.0 5.0 

Circulating turn (percent) 1.2 (76th percentile) 0.9 

Circulating yield (percent) 0.0 0.1 

Both the south and east legs are designated with lane-use markings on the approach as having 

two through lanes and a right-turn-only lane. However, for consistency with the single exit lane 

on the west leg and the striping within the roundabout, the east leg should be designated as leftturn-only, through-only, right-turn-only as soon as it completes its flaring from one to three lanes. 

Likewise, the south leg should be designated left-through, through-only, and right-turn only so 

that left-turning vehicles know to use the left lane. In both cases the left-turn arrow is omitted 

from the pavement markings in the left lane on the approach. No spiral markings or physical 

channelization is provided to guide the northbound and southbound left-turn movements into the 

outside circulating lane. 

39 
 

 

Geometrics may also be playing a factor. The elliptical shape of the roundabout creates a long 

section of circulatory roadway between the east entry and north exit, which makes it particularly 

difficult for drivers on the east leg to align properly with the circulatory roadway. The relatively 

narrow width of the circulatory roadway between these legs also makes it less comfortable for 

drivers to maintain lane position. The entry lanes on the south leg also misalign with the 

receiving circulating lanes. 

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Avon Rd./US 6, Avon, CO 

This roundabout, completed in 1997, is illustrated in figure 22. Observed volumes and erratic 

maneuvers are provided in table 10. 

Figure 22. Photo. Avon Rd./US 6, Avon, CO (Source: Google Maps 2015) 

Table 10. Observed Volumes and Erratic Maneuvers at Avon Rd./US 6, Avon, CO 

Observed Volume or Erratic Maneuver West Leg (Avon-3) North Leg (Avon-4) 

Approach volume (veh/h) 410 667 

Circulating volume (veh/h) 529 311 

Approach lane change (percent) 4.6 (82nd percentile) 2.2 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 0.9 14.8 (100th percentile) 

Circulating lane change (percent) 14.0 (100th percentile) 5.8 

Circulating turn (percent) 2.1 (79th percentile) 0.0 

Circulating yield (percent) 0.0 0.3 

Both the north and west legs have two-lane entries with the same lane use arrows: through and 

through-right. In both cases the left-turn arrow is omitted from the pavement markings in the left 

lane on the approach. However, the east and west legs are actually intended to have a left-turn 

only lane based on the single-lane exit on the opposite leg and the associated circulatory roadway 

pavement markings. This conflict shows in the high percentage of circulating straddles and 

circulating lane changes for the north leg, which reflects the similar challenge for drivers 

traveling as through movements from east to west. These lane designation inconsistencies are the 

likely causes of the observed erratic maneuvers. 

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Edwards Access Rd./Beard Creek Rd./I-70 WB Ramps, Edwards, CO 

This roundabout, completed in 2010, is illustrated in figure 23. Observed volumes and erratic 

maneuvers are provided in table 11. 

Figure 23. Photo. Edwards Access Rd./Beard Creek Rd./I-70 WB Ramps, Edwards, CO 

(Source: Google Earth 2011) 

Table 11. Observed Volumes and Erratic Maneuvers at Edwards Access Rd./Beard Creek 

Rd./I-70 WB Ramps, Edwards, CO 

Observed Volume or Erratic Maneuver North Leg (Edwards-1) East Leg (Edwards-2) 

Approach volume (veh/h) 692 217 

Circulating volume (veh/h) 224 417 

Approach lane change (percent) 2.6 0.9 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 1.8 0.0 

Circulating lane change (percent) 0.0 0.0 

Circulating turn (percent) 0.0 0.2 

Circulating yield (percent) 0.4 0.0 

Erratic maneuvers are notably low at this site. The geometry to guide northbound left turns into 

the outer lane appears smooth, and this is likely a cause of the low percentage of circulating 

straddles and lane changes at the north leg. 

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Edwards Access Rd./I-70 EB Ramps, Edwards, CO 

This roundabout, completed in 2010, is illustrated in figure 24. Observed volumes and erratic 

maneuvers are provided in table 12. 

Figure 24. Photo. Edwards Access Rd./I-70 EB Ramps, Edwards, CO (Source: Google 

Earth 2011) 

Table 12. Observed Volumes and Erratic Maneuvers at Edwards Access Rd. /I-70 EB 

Ramps, Edwards, CO 

Observed Volume or Erratic Maneuver West Leg (Edwards-4) 

Approach volume (veh/h) 657 

Circulating volume (veh/h) 397 

Approach lane change (percent) 0.8 

Approach turn (percent) 0.0 

Approach yield (percent) 0.0 

Circulating straddle (percent) 2.5 

Circulating lane change (percent) 3.0 

Circulating turn (percent) 0.3 

Circulating yield (percent) 0.0 

Erratic maneuvers are relatively low at this site. The straddles and lane changes may be due to 

positioning for downstream turning movements at the next roundabout, whose entrance line is 

only 230 feet downstream. 

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Edwards Access Rd./Miller Ranch Rd., Edwards, CO 

This roundabout, completed in 2010, is illustrated in figure 25. Observed volumes and erratic 

maneuvers are provided in table 13. 

Figure 25. Photo. Edwards Access Rd./Miller Ranch Rd., Edwards, CO (Source: Google 

Earth 2011) 

Table 13. Observed Volumes and Erratic Maneuvers at Edwards Access Rd./Miller Ranch 

Rd., Edwards, CO 

Observed Volume or Erratic Maneuver South Leg (Edwards-5) East Leg (Edwards-3) 

Approach volume (veh/h) 245 172 

Circulating volume (veh/h) 791 592 

Approach lane change (percent) 9.0 (95th percentile) 1.7 

Approach turn (percent) 0.0 3.5 (97th percentile) 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 3.0 0.0 

Circulating lane change (percent) 4.9 1.5 

Circulating turn (percent) 0.0 0.3 

Circulating yield (percent) 0.0 0.0 

The south leg experiences a high percentage of lane changes on the approach and a moderate 

percentage of circulating straddles and lane changes for the conflicting circulating movement. 

Each appears to be the outcome of drivers taking a fastest path with little potential conflict due to 

arriving as a single stream of vehicles. The conflicting circulating movement, occupied primarily 

by southbound left turns, is a wide single lane. 

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S. Golden Rd./Johnson St./16th Ave, Golden, CO 

This roundabout, completed in 1998, is illustrated in figure 26. Observed volumes and erratic 

maneuvers are provided in table 14. 

Figure 26. Photo. S. Golden Rd./Johnson St./16th Ave., Golden, CO (Source: Google Earth 

2014) 

Table 14. Observed Volumes and Erratic Maneuvers at S. Golden Rd./Johnson St./16th 

Ave., Golden, CO 

Observed Volume or Erratic Maneuver Southeast Leg (Golden-1) 

Approach volume (veh/h) 543 

Circulating volume (veh/h) 334 

Approach lane change (percent) 0.0 

Approach turn (percent) 0.0 

Approach yield (percent) 0.0 

Circulating straddle (percent) 2.1 

Circulating lane change (percent) 1.8 

Circulating turn (percent) 12.9 (100th percentile) 

Circulating yield (percent) 0.0 

The erratic maneuver of particular note at this site is the circulating turn maneuver in front of the 

southeast leg. Drivers making the southeast-bound left-turn movement from South Golden Road 

onto 16th Avenue who start (correctly) in the left entry lane to make a left-turn movement must 

then change lanes to exit onto 16th Avenue. To avoid changing lanes within the circulatory 

roadway, the drivers would need to incorrectly begin the left-turn movement from the right entry 

45 
 

 

lane, which conflicts with drivers making legal through movements from both entry lanes. This 

inconsistency between approach lane designation and circulating lane markings is the likely 

causes of the observed erratic maneuvers. 

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Table 15. Observed Volumes and Erratic Maneuvers at Hazel Dell Pkwy./126 th St., Carmel, IN 

 

 

 

 

 

Hazel Dell Pkwy./126th St., Carmel, IN 

This roundabout, completed in 1998, is illustrated in figure 27. Observed volumes and erratic 

maneuvers are provided in table 15. 

Figure 27. Photo. Hazel Dell Pkwy./126th St., Carmel, IN (Source: Google Earth 2012) 

Observed Volume or Erratic Maneuver East Leg (Carmel-3) North Leg (Carmel-4) 

Approach volume (veh/h) 118 127 

Circulating volume (veh/h) 1344 800 

Approach lane change (percent) 15.3 (100th percentile) 5.5 (87th percentile) 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 0.1 0.1 

Circulating lane change (percent) 0.0 4.8 

Circulating turn (percent) 0.1 0.0 

Circulating yield (percent) 0.1 0.0 

The large number of approach lane changes on the east leg is likely caused by the lane 

configuration of the entry, which requires drivers to use only the right lane to go through to a 

single-lane exit on the west leg. These lane changes also appear at a moderate level in the 

circulating lane changes in front of the north leg. Because the east leg flares from one to two 

lanes, the lane changes on the approach may be attributable to drivers not perceiving a conflict 

because the drivers are arriving in a single stream. Another contributing factor may be the use of 

only one set of lane control signs and lane use pavement markings within 100 ft of the 

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roundabout entry. The relatively high conflicting flow in this location may cause some drivers to 

queue up side-by-side regardless of destination and then change lanes once in the roundabout; 

this may explain some of the circulating lane changes. 

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Illinois St./116th St., Carmel, IN 

This roundabout, completed in 2005, is illustrated in figure 28. Observed volumes and erratic 

maneuvers are provided in table 16. 

Figure 28. Photo. Illinois St./116th St., Carmel, IN (Source: Google Earth 2012) 

Table 16. Observed Volumes and Erratic Maneuvers at Illinois St./116th St., Carmel, IN 

Observed Volume or Erratic Maneuver East Leg (Carmel-1) South Leg (Carmel-2) 

Approach volume (veh/h) 849 1585 

Circulating volume (veh/h) 231 545 

Approach lane change (percent) 0.6 2.0 

Approach turn (percent) 0.1 (84th percentile) 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 10.5 (97th percentile) 2.2 

Circulating lane change (percent) 6.1 0.7 

Circulating turn (percent) 0.0 0.4 

Circulating yield (percent) 0.0 0.0 

The most common erratic maneuvers observed at this site are circulating straddles and lane 

changes within the circulatory roadway in front of the east leg. The most likely cause of this is 

the low circulating flow during the observed period. Drivers under these flow conditions likely 

were not traveling next to other vehicles and thus could straddle or change lanes with little 

consequence. Another possible cause is geometric. There appears to be a minor amount of path 

misalignment on the entries and exits that could guide drivers from the right entry lane on the 

south leg to the left circulating lane and then to the right exiting lane on the north leg. 

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SR 67/Blacksmith Dr./Kelch Dr., Malta, NY 

This roundabout, completed in 2006, is illustrated in figure 29. Observed volumes and erratic 

maneuvers are provided in table 17. 

Figure 29. Photo. SR 67/Blacksmith Dr./Kelch Dr., Malta, NY (Source: Google Earth 2013) 

Table 17. Observed Volumes and Erratic Maneuvers at SR 67/Blacksmith Dr./Kelch Dr., 

Malta, NY 

Observed Volume or Erratic Maneuver East Leg (Malta-10) West Leg (Malta-09) 

Approach volume (veh/h) 495 541 

Circulating volume (veh/h) 106 53 

Approach lane change (percent) 7.1 (92nd percentile) 1.5 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.1 0.1 

Circulating straddle (percent) 8.5 (89th percentile) 6.4 (82nd percentile) 

Circulating lane change (percent) 10.4 (89th percentile) 11.0 (92nd percentile) 

Circulating turn (percent) 0.9 7.5 (95th percentile) 

Circulating yield (percent) 0.0 0.0 

This experiences a high percentage of circulating straddles and lane changes in front of the east 

and west legs, as well as a relatively high percentage of approach lane changes on the east leg. 

This roundabout is located immediately east of the SR 67/I-87 interchange, and drivers intending 

to go north on I-87 would need to be in the right lane to use the on-ramp. If these drivers started 

their left turn at SR 67/Kelch Drive from the left lane, they would need to change lanes 

somewhere to position themselves correctly. There were also some observations of drivers 

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entering from the south in the left lane and exiting to the north, changing lanes to exit (recorded 

as a circulating lane change in front of the east leg). 

For the west leg, the observed circulating volumes were relatively low. Some drivers making a 

westbound left turn turned from the outside lane, and others straddled the hatched spiral area 

next to the truck apron. These conflicts may be the product of some confusion about the spiral 

marking. 

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Table 18. Observed Volumes and Erratic Maneuvers at SR 67/I-87 SB Ramps, Malta, NY 

 

 

 

SR 67/I-87 SB Ramps, Malta, NY 

This roundabout, completed in 2006, is illustrated in figure 30. Observed volumes and erratic 

maneuvers are provided in table 18. 

Figure 30. Photo. SR 67/I-87 SB Ramps, Malta, NY (Source: Google Earth 2013) 

Observed Volume or Erratic Maneuver East Leg (Malta-02) West Leg (Malta-03) 

Approach volume (veh/h) 950 393 

Circulating volume (veh/h) 34 389 

Approach lane change (percent) 0.6 2.3 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.3 0.5 

Circulating straddle (percent) 0.0 7.0 (84th percentile) 

Circulating lane change (percent) 0.0 8.2 (79th percentile) 

Circulating turn (percent) 0.0 0.0 

Circulating yield (percent) 0.0 0.0 

The most common erratic maneuvers at this location are circulating straddles and lane changes in 

front of the west leg. These are primarily caused by westbound drivers intending to turn left onto 

the on-ramp, hugging the truck apron instead of following the spiral striping, and then either 

straddling the spiral striping or being forced to change lanes to exit. 

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SR 67/I-87 NB Ramps, Malta, NY 

This roundabout, completed in 2006, is illustrated in figure 31. Observed volumes and erratic 

maneuvers are provided in table 19. 

Figure 31. Photo. SR 67/I-87 NB Ramps, Malta, NY (Source: Google Earth 2013) 

Table 19. Observed Volumes and Erratic Maneuvers at SR 67/I-87 NB Ramps, Malta, NY 

Observed Volume or Erratic Maneuver East Leg (Malta-05) West Leg (Malta-04) 

Approach volume (veh/h) 350 703 

Circulating volume (veh/h) 859 47 

Approach lane change (percent) 2.9 1.4 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.4 0.5 

Circulating straddle (percent) 5.0 (76th percentile) 0.0 

Circulating lane change (percent) 8.0 (76th percentile) 9.0 (84th percentile) 

Circulating turn (percent) 0.0 8.0 (97th percentile) 

Circulating yield (percent) 0.0 0.0 

The geometry here is similar to that at SR 67/I-87 SB Ramps, and as a result the pattern of erratic 

maneuvers is similar. The most common erratic maneuvers are primarily caused by drivers 

intending to turn left onto the on-ramp or making a U-turn in front of the west leg, hugging the 

truck apron instead of following the spiral striping, and then either straddling the spiral striping 

or being forced to change lanes to exit. 

53 
 

 

 

SR 67/US 9, Malta, NY 

This roundabout, completed in 2006, is illustrated in figure 32. Observed volumes and erratic 

maneuvers are provided in table 20. 

Figure 32. Photo. SR 67/US 9, Malta, NY (Source: Google Earth 2013) 

Table 20. Observed Volumes and Erratic Maneuvers at SR 67/US 9, Malta, NY 

Observed Volume or Erratic Maneuver East Leg (Malta-06) West Leg (Malta-01) 

Approach volume (veh/h) 343 682 

Circulating volume (veh/h) 709 496 

Approach lane change (percent) 0.9 0.7 

Approach turn (percent) 0.0 0.1 (89th percentile) 

Approach yield (percent) 0.3 0.2 

Circulating straddle (percent) 2.0 2.8 

Circulating lane change (percent) 6.0 4.4 

Circulating turn (percent) 3.0 (87th percentile) 0.8 

Circulating yield (percent) 0.0 0.0 

This roundabout experienced relatively few erratic maneuvers, with the most common being 

circulating lane changes in front of the east leg. The circulating turn erratic maneuvers in front of 

the east leg are likely due to the westbound left-turn-only lane that requires northbound left turns 

to shift to the outside circulating lane to exit to the west. 

54 
 

 

 

 

SR 67/State Farm Blvd., Malta, NY 

This roundabout, completed in 2006, is illustrated in figure 33. Observed volumes and erratic 

maneuvers are provided in table 21. 

Figure 33. Photo. SR 67/State Farm Blvd., Malta, NY (Source: Google Earth 2013) 

Table 21. Observed Volumes and Erratic Maneuvers at SR 67/State Farm Blvd., Malta, NY 

Observed Volume or Erratic Maneuver East Leg (Malta-07) West Leg (Malta-08) 

Approach volume (veh/h) 682 602 

Circulating volume (veh/h) 73 127 

Approach lane change (percent) 2.1 6.0 (89th percentile) 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.4 0.4 

Circulating straddle (percent) 0.0 7.0 (84th percentile) 

Circulating lane change (percent) 0.0 12.0 (95th percentile) 

Circulating turn (percent) 0.0 0.0 

Circulating yield (percent) 0.0 0.0 

This roundabout experienced a relatively high percentage of approach lane changes on the west 

leg, as well as a high percentage of circulating straddles and lane changes in front of the west leg. 

The circulating erratic maneuvers appear to be caused by (1) drivers incorrectly making a 

through movement in the southbound direction from the left lane and (2) drivers making a 

westbound left turn and not picking up on the spiral striping that guides them to the outside 

circulating lane. The likely cause for the approach lane changes on the west leg is not readily 

apparent. 

55 
 

 

 

 

 

14th Ave./Jefferson St., Olympia, WA 

This roundabout, completed in 2010, is illustrated in figure 34. Observed volumes and erratic 

maneuvers are provided in table 22. 

Figure 34. Photo. 14th Ave./Jefferson St., Olympia, WA (Source: Google Earth 2013) 

Table 22. Observed Volumes and Erratic Maneuvers at 14th Ave./Jefferson St., Olympia, WA 

Observed Volume or Erratic Maneuver North Leg (Olympia-2) South Leg (Olympia-4) 

Approach volume (veh/h) 642 209 

Circulating volume (veh/h) 704 718 

Approach lane change (percent) 1.7 1.0 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 9.2 (92nd percentile) 0.0 

Circulating lane change (percent) 3.8 0.0 

Circulating turn (percent) 0.1 0.0 

Circulating yield (percent) 0.1 0.0 

The only erratic maneuver of significance at this roundabout are the circulating lane straddles in 

front of the north leg. The likely cause of these lane straddles is a slight geometric misalignment 

of the east leg entry with its receiving section of circulatory roadway in front of the north leg. 

The right entry lane aims partially into the left circulating lane. 

56 
 

 

 

 

4th Ave./Olympic Way, Olympia, WA 

This roundabout, completed in 2004, is illustrated in figure 35. Observed volumes and erratic 

maneuvers are provided in table 23. 

Figure 35. Photo. 4th Ave./Olympic Way, Olympia, WA (Source: Google Earth 2013) 

Table 23. Observed Volumes and Erratic Maneuvers at 4th Ave./Olympic Way, Olympia, WA 

Observed Volume or Erratic Maneuver South Leg (Olympia-1) East Leg (Olympia-3) 

Approach volume (veh/h) 532 1078 

Circulating volume (veh/h) 812 538 

Approach lane change (percent) 3.9 1.0 

Approach turn (percent) 0.0 0.1 (82nd percentile) 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 0.0 0.0 

Circulating lane change (percent) 0.0 4.5 

Circulating turn (percent) 0.1 0.4 

Circulating yield (percent) 0.0 0.0 

The most significant erratic maneuver observed at this roundabout are the circulating lane 

changes in front of the east leg. The likely cause of these lane straddles is the long section of 

circulatory roadway between the east and south legs, which is caused by the skew of the 

intersection, and the relatively small exit radius leading to the north exit. 

57 
 

 

 

 

Borgen Blvd./51st Ave. NW, Gig Harbor, WA 

This roundabout, completed in 2002, is illustrated in figure 36. Observed volumes and erratic 

maneuvers are provided in table 24. 

Figure 36. Photo. Borgen Blvd./51st Ave. NW, Gig Harbor, WA (Source: Google Earth 

2015) 

Table 24. Observed Volumes and Erratic Maneuvers at Borgen Blvd./51st Ave. NW, Gig 

Harbor, WA 

Observed Volume or Erratic Maneuver East Leg (Gig Harbor-2) 

Approach volume (veh/h) 1002 

Circulating volume (veh/h) 229 

Approach lane change (percent) 1.2 

Approach turn (percent) 0.0 

Approach yield (percent) 0.0 

Circulating straddle (percent) 6.0 (79th percentile) 

Circulating lane change (percent) 10.0 (87th percentile) 

Circulating turn (percent) 3.6 (89th percentile) 

Circulating yield (percent) 0.0 

The most significant erratic maneuvers observed at this roundabout are the circulating straddles, 

lane changes, and turns in front of the east leg. These are caused primarily by the spiraling 

alignment of the circulatory roadway in front of the east leg. Drivers have worn off the spiral 

pavement markings next to the truck apron and then when exiting to the north, they cross the 

circulating lane striping in front of the north leg that is receiving westbound through movements. 

58 
 

Harbor Hill Dr./Development Entrance, Gig Harbor, WA 

This roundabout, completed in 2008, is illustrated in figure 37. Observed volumes and erratic 

maneuvers are provided in table 25. 

Figure 37. Photo. Harbor Hill Dr./Development Entrance, Gig Harbor, WA (Source: 

Google Earth 2015) 

Table 25. Observed Volumes and Erratic Maneuvers at Harbor Hill Dr./Development 

Entrance, Gig Harbor, WA 

Observed Volume or Erratic Maneuver North Leg (Gig Harbor-1) 

Approach volume (veh/h) 318 

Circulating volume (veh/h) 69 

Approach lane change (percent) 2.5 

Approach turn (percent) 0.0 

Approach yield (percent) 0.0 

Circulating straddle (percent) 0.0 

Circulating lane change (percent) 0.0 

Circulating turn (percent) 0.0 

Circulating yield (percent) 0.0 

Few significant erratic maneuvers were observed at this roundabout. The approach lane changes 

were caused by the dedicated right-turn lane. 

59 
 

SR 539/Pole Rd., Lynden (Whatcom County), WA 

This roundabout, completed in 2009, is illustrated in figure 38. Observed volumes and erratic 

maneuvers are provided in table 26. 

Figure 38. Photo. SR 539/Pole Rd., Lynden (Whatcom County), WA (Source: Google Earth 

2015) 

Table 26. Observed Volumes and Erratic Maneuvers at SR 539/Pole Rd., Lynden 

(Whatcom County), WA 

Observed Volume or Erratic Maneuver North Leg (Lynden-1) South Leg (Lynden-3) 

Approach volume (veh/h) 632 808 

Circulating volume (veh/h) 144 26 

Approach lane change (percent) 0.6 1.0 

Approach turn (percent) 0.2 (92nd percentile) 0.0 

Approach yield (percent) 0.0 0.0 

Circulating straddle (percent) 0.0 0.0 

Circulating lane change (percent) 0.0 0.0 

Circulating turn (percent) 2.1 (82nd percentile) 0.0 

Circulating yield (percent) 1.4 0.0 

Few erratic maneuvers were observed at this roundabout. 

60 
 

 

 

SR 539/Ten Mile Rd., Lynden (Whatcom County), WA 

This roundabout, completed in 2009, is illustrated in figure 39. Observed volumes and erratic 

maneuvers are provided in table 27. 

Figure 39. Photo. SR 539/Ten Mile Rd., Lynden (Whatcom County), WA (Source: Google 

Earth 2015) 

Table 27. Observed Volumes and Erratic Maneuvers at SR 539/Ten Mile Rd. , Lynden 

(Whatcom County), WA 

Observed Volume or Erratic Maneuver South Leg (Lynden-4) 

Approach volume (veh/h) 688 

Circulating volume (veh/h) 47 

Approach lane change (percent) 0.0 

Approach turn (percent) 0.1 (87th percentile) 

Approach yield (percent) 0.0 

Circulating straddle (percent) 0.0 

Circulating lane change (percent) 0.0 

Circulating turn (percent) 4.3 (92nd percentile) 

Circulating yield (percent) 0.0 

The most significant erratic maneuver observed at this roundabout are the circulating turns in 

front of the south leg. These are most likely caused by drivers making a southbound left turn by 

starting from the right entry lane so that they are aligned into the outer circulating lane. 

61 
 

 

SR 539/Wiser Lake Rd., Lynden (Whatcom County), WA 

This roundabout, completed in 2009, is illustrated in figure 40. Observed volumes and erratic 

maneuvers are provided in table 28. 

Figure 40. Photo. SR 539/Wiser Lake Rd., Lynden (Whatcom County), WA (Source: 

Google Earth 2015) 

Table 28. Observed Volumes and Erratic Maneuvers at SR 539/Wiser Lake Rd., Lynden, 

(Whatcom County) WA 

Observed Volume or Erratic Maneuver North Leg (Lynden-2) 

Approach volume (veh/h) 613 

Circulating volume (veh/h) 160 

Approach lane change (percent) 1.0 

Approach turn (percent) 0.0 

Approach yield (percent) 0.0 

Circulating straddle (percent) 0.0 

Circulating lane change (percent) 0.0 

Circulating turn (percent) 0.0 

Circulating yield (percent) 0.0 

Very few erratic maneuvers were observed at this roundabout. 

62 
 

Jackson St./Murdock Ave., Oshkosh, WI 

This roundabout, completed in 2010, is illustrated in figure 41. Observed volumes and erratic 

maneuvers are provided in table 29. 

Figure 41. Photo. Jackson St./Murdock Ave., Oshkosh, WI (Source: Google Earth 2015) 

Table 29. Observed Volumes and Erratic Maneuvers at Jackson St./Murdock Ave., 

Oshkosh, WI 

Observed Volume or Erratic Maneuver East Leg (Oshkosh-2) West Leg (Oshkosh-1) 

Approach volume (veh/h) 448 602 

Circulating volume (veh/h) 593 729 

Approach lane change (percent) 1.8 0.0 

Approach turn (percent) 0.0 0.0 

Approach yield (percent) 0.0 0.2 

Circulating straddle (percent) 3.0 0.0 

Circulating lane change (percent) 8.2 (79th percentile) 2.4 

Circulating turn (percent) 0.0 0.2 

Circulating yield (percent) 0.1 0.1 

The most significant erratic maneuver observed at this roundabout are the circulating lane 

changes in front of the east leg. The causes of these lane changes are most likely due to 

positioning for downstream destinations; the nearest intersections or entrances to left turn 

pockets are less than 150 ft away from the roundabout. 

63 
 

Main St./Cemetery Rd., Hilliard, OH 

This roundabout, completed in 2009, is illustrated in figure 42. Observed volumes and erratic maneuvers are provided in table 30. 

Figure 42. Photo. Main St./Cemetery Rd., Hilliard, OH (Source: Google Earth 2014) 

64 
Table 30. Observed Volumes and Erratic Maneuvers at Main St./Cemetery Rd., Hilliard, OH 

Time 

Period 

Approach 

Volume 

(vph) 

Approach 

Lane 

Change 

(vph) 

Approach 

Straddle 

(vph) 

Approach 

Turn 

(vph) 

Approach 

Yield 

(vph) 

Circulating 

Volume 

(vph) 

Circulating 

Lane 

Change 

(vph) 

Circulating 

Straddle 

(vph) 

Circulating 

Turn 

(vph) 

Circulating 

Yield 

(vph) 

630-730 252 5 0 0 3 160 2 4 0 0 

730-830 636 0 0 0 3 296 7 4 0 0 

830-930 464 3 1 0 1 400 11 4 1 0 

930-1030 276 1 2 2 0 352 6 5 0 0 

1030-1130 284 1 1 1 2 392 17 4 0 0 

1130-1230 316 2 1 3 3 520 20 4 2 0 

1230-1330 368 2 0 0 2 612 10 3 1 0 

1330-1430 304 2 0 1 0 496 7 2 0 0 

1430-1530 468 0 0 2 2 504 9 1 0 0 

1530-1630 356 0 0 0 1 668 5 1 0 0 

1630-1730 408 2 0 0 6 780 5 1 2 0 

1730-1830 356 1 0 0 3 896 10 1 0 1 

1830-1930 356 1 0 1 3 632 14 0 0 0 

Total 4,844 20 5 10 29 6,708 123 34 6 1 

65 
 

Main St./Scioto Darby Rd., Hilliard, OH 

This roundabout, completed in 2009, is illustrated in figure 43. Observed volumes and erratic maneuvers are provided in table 31. 

Figure 43. Photo. Main St./Scioto Darby Rd., Hilliard, OH (Source: Google Earth 2014) 

66 
 

Table 31. Observed Volumes and Erratic Maneuvers at Main St./Scioto Darby Rd., Hilliard, OH 

Time 

Period 

Approach 

Volume 

(vph) 

Approach 

Lane 

Change 

Approach 

Straddle 

Approach 

Turn 

Approach 

Yield 

Circulating 

Volume 

(vph) 

Circulating 

Lane 

Change 

Circulating 

Straddle 

Circulating 

Turn 

Circulating 

Yield 

630-730 88 3 0 0 0 592 4 10 0 0 

730-830 144 0 0 0 1 1,240 1 23 0 1 

830-930 248 2 2 0 3 808 2 22 0 1 

930-1030 92 0 0 0 0 580 6 26 0 0 

1030-1130 96 5 0 0 1 600 4 19 0 1 

1130-1230 152 0 0 0 2 704 3 20 0 1 

1230-1330 208 0 0 0 0 872 1 22 0 0 

1330-1430 180 1 0 0 1 764 4 13 0 0 

1430-1530 276 2 0 0 1 756 2 11 0 0 

1530-1630 376 4 1 0 1 892 4 14 0 0 

1630-1730 384 5 0 0 0 816 3 7 0 0 

1730-1830 412 2 2 0 1 1,044 8 8 0 0 

1830-1930 280 2 0 0 0 1,016 3 11 0 0 

Total 2,936 26 5 0 11 10,684 45 206 0 4 

67 

 

 

 

 

 

 

 

 

APPENDIX B. EYE TRACKER STUDY POST-DRIVE QUESTIONNAIRE 

Date: 

Time: 

Subject Number: 

1. How many years have you been driving in the United States? (less than 5 years, between 

5 and 10 years, between 10 and 20 years, and more than 20 years) 

2. How many hours a day do you drive? (less than an hour, between 1 and 2 hours, more 

than 2 hours) 

3. How many times a week do you drive through a roundabout (or multiple roundabouts)? 

(less than once a week, between 1 and 555 times a week, more than 5 times a week) 

4. Do you drive through a single-lane or a multi-lane roundabout? (single-lane, multi-lane, 

both) 

5. I am comfortable navigating through roundabouts. (strongly disagree, disagree, 

neutral/don’t know, agree, strongly agree) 

6. I am comfortable negotiating traffic and choosing my lane at the entry of a roundabout. 

(strongly disagree, disagree, neutral/don’t know, agree, strongly agree) 

7. I am comfortable negotiating traffic and choosing my lane in the circulating lanes of a 

roundabout. (strongly disagree, disagree, neutral/don’t know, agree, strongly agree) 

8. I am comfortable negotiating traffic and choosing my lane at the exit of a roundabout. 

(strongly disagree, disagree, neutral/don’t know, agree, strongly agree) 

9. Signs help me navigate as I approach and drive through a roundabout. (strongly disagree, 

disagree, neutral/don’t know, agree, strongly agree) 

10. Pavement markings help me navigate as I approach and drive through a roundabout. 

(strongly disagree, disagree, neutral/don’t know, agree, strongly agree) 

11. Which of the following do you pay more attention to as you approach and drive through 

the roundabouts? (signs along the way to the roundabout, in circulating lanes, and upon 

exiting; pavement markings and lane striping on the approach and in the circulating lanes; 

both; neither; I take a guess or I know my way) 

69 

 

 

 

 

APPENDIX C. EYE TRACKER STUDY QUESTIONNAIRE RESULTS 

The results of the eye-tracking study questionnaire are shown in figure 40 through figure 50. 

Figure 44. Chart. Questionnaire results for “How many hours a day do you drive?” 

Figure 45. Chart. Questionnaire results for “How many years have you been driving in the 

United States?” 

71 
 

 

Figure 46. Chart. Questionnaire results for “Do you drive through a single-lane or a multilane roundabout?” 

Figure 47. Chart. Questionnaire results for “How many times a week do you drive through 

a roundabout (or multiple roundabouts)?” 

72 
 

 

Figure 48. Chart. Questionnaire results for “I am comfortable negotiating traffic and 

choosing my lane at the entry of a roundabout.” 

Figure 49. Chart. Questionnaire results for “I am comfortable navigating through 

roundabouts.” 

73 
 

 

 

 

Figure 50. Chart. Questionnaire results for “I am comfortable negotiating and choosing my 

lane at the exit of a roundabout.” 

Figure 51. Chart. Questionnaire results for “I am comfortable negotiating and choosing my 

lane in the circulating lanes of a roundabout.” 

74 
Figure 52. Chart. Questionnaire results for “Pavement markings help me navigate as I 

approach and drive through a roundabout.” 

Figure 53. Chart. Questionnaire results for “Signs help me as I approach and drive 

through a roundabout.” 

75 
Figure 54. Chart. Questionnaire results for “Which of the following do you pay more 

attention to as you approach and drive through the roundabouts?” 

76 
77 

APPENDIX D. EYE-TRACKER STUDY MANEUVERS (HILLIARD, OH)

The maneuvers performed by the participant drivers at each of the roundabouts in Hilliard, OH, 

are shown in figure 51, figure 52, figure 53, figure 54, figure 55, and figure 56. 

Figure 55. Diagrams. Hilliard OH roundabout - Main St. and Scioto Darby St.
78 

Figure 56. Diagrams. Hilliard OH roundabout - Main St. and Cemetery Rd.
79 

Figure 57. Diagrams. Hilliard OH roundabout - Main St., Cemetery Rd., and Scioto Darby 

Rd.
80 

Figure 58. Diagrams. Hilliard, OH roundabout - Leap Rd. and Anson Dr.

Figure 59. Diagrams. Hilliard, OH roundabout – Britton Pkwy and Anson Dr.
81 

Figure 60. Diagram. Hilliard, OH roundabout – Britton Pkwy and Davidson Rd.

83 

Figure 61. Diagrams. Carmel, IN roundabout – Old Meridian St. and Grand Blvd.

APPENDIX E. EYE-TRACKER STUDY MANEUVERS (CARMEL, IN)

The maneuvers performed by the participant drivers at each of the roundabouts in Carmel, IN are 

shown in figure 57, figure 58, figure 59, and figure 60. 
84 

Figure 62. Diagrams. Carmel, IN roundabout – Old Meridian St. and N. Pennsylvania St.

Figure 63. Carmel, IN roundabout – Clay Terrace Blvd, North Roundabout.
85 

Figure 64. Carmel, IN roundabout – Clay Terrace Blvd, South Roundabout.

87 

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4. Molino, J. A., B. J. Katz, V. W. Inman, and A. Emo. “Lane Restriction Signing and Marking

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Research Board 2014 Annual Meeting, Transportation Research Board, 2014, 20p.

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