Accelerating Roundabout Implementation 

in the United States – Volume IV of VII 

A Review of Fatal and Severe Injury 

Crashes at Roundabouts 

PUBLICATION NO. FHWA-SA-15-072 SEPTEMBER 2015 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

FOREWORD 

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. 

i 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TECHNICAL REPORT DOCUMENTATION PAGE 

1. Report No. 

FHWA-SA-15-072 

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

4. Title and Subtitle 

Accelerating Roundabouts in the United States: Volume IV of VII 

– A Review of Fatal and Severe Injury Crashes at Roundabouts 

5. Report Date 

September 2015 

6. Performing Organization Code: 

7. Author(s) 

Steyn, Hermanus J.; Ashleigh Griffin; and Lee A. 

Rodegerdts

8. Performing Organization Report No. 

11861 Task 5 

9. Performing Organization Name and Address 

Kittelson & Associates, Inc., 610 SW Alder St. Suite 700, 

Portland, OR 97205

10. Work Unit No. (TRAIS) 

11. Contract or Grant No. 

DTFH61-10-D-00023-T-11002 

12. Sponsoring Agency Name and Address 

Office of Safety 

Federal Highway Administration 

United States Department of Transportation 

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 fourth in a series of seven. The other volumes in the series are: Volume I - Evaluation of Rectangular RapidFlashing 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 V – 

Evaluation of Geometric Parameters that Affect Truck Maneuvering and Stability, Volume VI – Investigation of Crosswalk 

Design and Driver Behaviors, and Volume VII – Human Factor Assessment of Traffic Control Device Effectiveness. 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 summarizes the review of fatal crashes at roundabouts in the United States known to the team through December 

2013, along with a sample of injury crashes from the States of Washington and Wisconsin. The information summarized in 

this report focuses on crash characteristics and harmful events to determine whether there are elements of roundabout design 

practice that can be modified to reduce the likelihood of a fatality or severe injury even further. Crash types found to be 

overrepresented include motorcycle crashes, fixed object crashes, and crashes involving impaired driving. Attention to curb 

design, particularly at the interior edge of the truck apron and the splitter island; increased visibility of the intersection; and 

attention to the placement and protection of fixed objects have the potential to reduce fatal and severe injury crashes. 

Continued emphasis on driver education and enforcement is also recommended to address the large number of crashes 

involving impaired drivers. 

17. Key Words 

Roundabouts, crash, fatal, injury, countermeasure, 

safety 

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 

64 

22. Price 

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

ii 
TABLE OF CONTENTS 

FOREWORD.................................................................................................................................. i 

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

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

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

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

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

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

CHAPTER 2. NATIONAL AND STATE CRASH BENCHMARKS ..................................... 3 

CHAPTER 3. CRASH HISTORY REVIEW............................................................................. 9 

FATAL CRASH REVIEW ...................................................................................................... 9 

Fatal Crash Data ................................................................................................................... 9 

Characteristics of Fatal Crashes at Roundabouts ........................................................... 10 

INJURY CRASH REVIEW................................................................................................... 13 

Injury Crash Data............................................................................................................... 13 

Washington...................................................................................................................... 13 

Wisconsin......................................................................................................................... 13 

SUMMARY OF CRASH TRENDS ...................................................................................... 18 

Major Trends ...................................................................................................................... 18 

CHAPTER 4. CONCLUSIONS AND RECOMMENDATIONS ........................................... 23 

FIXED OBJECTS................................................................................................................... 23 

Curbs.................................................................................................................................... 23 

Rigid Fixed Objects............................................................................................................. 24 

MOTORCYCLES................................................................................................................... 24 

VISIBILITY AND CONSPICUITY...................................................................................... 24 

EDUCATION AND ENFORCEMENT................................................................................ 25 

ADDITIONAL RECOMMENDATIONS............................................................................. 25 

REFERENCES............................................................................................................................ 27 

APPENDIX A. FATAL CRASH DATA ................................................................................... 29 

APPENDIX B: INJURY CRASH DATA TRENDS ................................................................ 33 

INJURY SEVERITY.............................................................................................................. 33 

TIME OF DAY........................................................................................................................ 34 

iii 
 

 

WEATHER.............................................................................................................................. 36 

LIGHT CONDITIONS........................................................................................................... 38 

VEHICLE TYPE .................................................................................................................... 40 

ALCOHOL INVOLVEMENT .............................................................................................. 42 

NUMBER OF VEHICLES INVOLVED.............................................................................. 44 

ALCOHOL INVOLVEMENT AND NUMBER OF VEHICLES INVOLVED ............... 46 

NUMBER OF VEHICLES INVOLVED AND VEHICLE TYPE ..................................... 48 

CRASH TYPE......................................................................................................................... 50 

OBJECTS STRUCK............................................................................................................... 52 

CONTRIBUTING CIRCUMSTANCES .............................................................................. 53 

JUNCTION RELATION BY VEHICLE TYPE.................................................................. 54 

PEDESTRIAN AND BICYCLIST CRASHES .................................................................... 55 

iv 
 

 

 

 

 

 

 

 

LIST OF FIGURES 

Figure 1. Diagram. Key characteristics of modern roundabouts. ............................................ 1 

Figure 4. Chart. Estimated Number of Fatal Crashes per Roundabout in the United States 

Figure 9. Chart. Number of crashes by injury severity, Washington; “PDO” stands for 

Figure 10. Chart. Number of crashes by injury severity, Wisconsin. “PDO” stands for 

Figure 2. Chart. Number of Fatal Crashes at Roundabouts in the U.S. by Year. ................ 10 

Figure 3. Chart. Estimated Number of Roundabouts in the U.S. by Year............................ 11 

by Year. ........................................................................................................................................ 11 

Figure 5. Chart. Percent of crashes that were single-vehicle crashes. ................................... 18 

Figure 6. Chart. Percent of crashes involving motorcycles. .................................................... 19 

Figure 7. Chart. Percent of crashes involving impaired driving. ........................................... 20 

Figure 8. Chart. Percent of crashes involving vehicles hitting the curb. ............................... 21 

“property damage only.” ............................................................................................................ 33 

“property damage only.” ............................................................................................................ 33 

Figure 11. Chart. Time of day for all injury crashes, Washington. ....................................... 34 

Figure 12. Chart. Time of day for injury A and B crashes, Washington. ............................. 34 

Figure 13. Chart. Time of day for all injury crashes, Wisconsin. .......................................... 35 

Figure 14. Chart. Time of day for injury A and B crashes, Wisconsin.................................. 35 

Figure 15. Chart. Weather, all injury crashes, Washington. .................................................. 36 

Figure 16. Chart. Weather, for injury A and B crashes, Washington. .................................. 36 

Figure 17. Chart. Weather, for all injury crashes, Wisconsin................................................ 37 

Figure 18. Chart. Weather, for injury A and B crashes, Wisconsin. ..................................... 37 

Figure 19. Chart. Light conditions for all injury crashes, Washington. ................................ 38 

Figure 20. Chart. Light conditions for injury A and B crashes, Washington. ...................... 38 

Figure 21. Chart. Light conditions for all injury crashes, Wisconsin.................................... 39 

Figure 22. Chart. Light conditions for injury A and B crashes, Wisconsin. ......................... 39 

Figure 23. Chart. Vehicle type for all injury crashes, Washington. ....................................... 40 

Figure 24. Chart. Vehicle type for all injury A and B crashes, Washington. ........................ 40 

Figure 25. Chart. Vehicle type for all injury crashes, Wisconsin........................................... 41 

Figure 26. Chart. Vehicle type for injury A and B crashes, Wisconsin................................. 41 

Figure 27. Chart. Alcohol involvement for all injury crashes, Washington. ......................... 42 

Figure 28. Chart. Alcohol involvement in injury A and B crashes, Washington.................. 42 

Figure 29. Chart. Alcohol involvement in all injury crashes, Wisconsin............................... 43 

v 
 

 

 

 

 

 

 

 

 

 

 

Figure 30. Chart. Alcohol involvement in injury A and B crashes, Wisconsin..................... 43 

Figure 35. Chart. Alcohol involvement and number of vehicles involved, all injury crashes, 

Figure 36. Chart. Alcohol involvement and number of vehicles involved, injury A and B 

Figure 37. Chart. Alcohol involvement and number of vehicles involved, all injury crashes, 

Figure 38. Chart. Alcohol involvement and number of vehicles involved, injury A and B 

Figure 39. Chart. Number of vehicles involved and vehicle type, all injury crashes, 

Figure 40. Chart. Number of vehicles involved and vehicle type, injury A and B crashes, 

Figure 41. Chart. Number of vehicles involved and vehicle type, all injury crashes, 

Figure 42. Chart. Number of vehicles involved and vehicle type, Injury A and B crashes, 

Figure 49. Chart. Contributing circumstances for all injury crashes involving vehicles 

Figure 50. Chart. Contributing circumstances for all injury A and B crashes involving 

Figure 31. Chart. Number of vehicles involved, all injury crashes, Washington. ................ 44 

Figure 32. Chart. Number of vehicles involved, injury A and B crashes, Washington. ....... 44 

Figure 33. Chart. Number of vehicles involved, all injury crashes, Wisconsin..................... 45 

Figure 34. Chart. Number of vehicles involved, injury A and B crashes, Wisconsin. .......... 45 

Washington.................................................................................................................................. 46 

crashes, Washington. .................................................................................................................. 46 

Wisconsin..................................................................................................................................... 47 

crashes, Wisconsin. ..................................................................................................................... 47 

Washington.................................................................................................................................. 48 

Washington.................................................................................................................................. 48 

Wisconsin..................................................................................................................................... 49 

Wisconsin..................................................................................................................................... 49 

Figure 43. Chart. Crash type for all injury crashes, Washington. ......................................... 50 

Figure 44. Chart. Crash type for all Injury A and B crashes, Washington. ......................... 50 

Figure 45. Chart. Crash type for all injury crashes, Wisconsin............................................. 51 

Figure 46. Chart. Crash type for injury A and B crashes, Wisconsin. .................................. 51 

Figure 47. Chart. First and second objects struck, all injury crashes, Washington............. 52 

Figure 48. Chart. First and second objects struck, injury A and B crashes, Washington... 52 

hitting the curb, Washington. .................................................................................................... 53 

vehicles hitting the curb, Washington....................................................................................... 53 

Figure 51. Chart. Junction relation by vehicle type, all injury crashes, Washington. ......... 54 

Figure 52. Chart. Junction relation by vehicle type, injury A and B crashes, Washington. 54 

Figure 53. Chart. Pedestrian and bicyclist crashes, all injury crashes, Washington. .......... 55 

Figure 54. Chart. Pedestrian and bicyclist crashes, injury A and B crashes, Washington. . 55 

Figure 55. Chart. Pedestrian and bicyclist crashes, all injury crashes, Wisconsin............... 56 

vi 
Figure 56. Chart. Pedestrian and bicyclist crashes, injury A and B crashes, Wisconsin. .... 56 

vii 
 

 

 

LIST OF TABLES 

Table 1. Number of Fatalities in the United States in 2012....................................................... 3 

Table 2. Summary of fatal crash characteristics.(3) ................................................................... 5 

Table 3. Percentage of serious injuries by State by crash factor.............................................. 8 

Table 4. Summary of characteristics of fatal crashes at roundabouts in the United States. 12 

Table 5. Summary of crash type trends in injury crashes at roundabouts in Washington 

and Wisconsin. ............................................................................................................................ 15 

Table 6. Summary of vehicle and participant type trends in injury crashes at roundabouts 

in Washington and Wisconsin. .................................................................................................. 16 

Table 7. Summary of injury crashes involving impaired driving at roundabouts in 

Washington and Wisconsin........................................................................................................ 16 

Table 8. Summary of light conditions in injury crashes at roundabouts in Washington and 

Wisconsin..................................................................................................................................... 17 

Table 9. Summary of weather conditions in injury crashes at roundabouts in Washington 

and Wisconsin. ............................................................................................................................ 17 

Table 10. Fatal crash data. ......................................................................................................... 29 

viii 
 

 

 

 

 

 

 

 

 

 

 

CHAPTER 1. INTRODUCTION 

This report summarizes the review of fatal and injury crashes at roundabouts in the United 

States. A roundabout is a form of circular intersection in which traffic travels counterclockwise 

in the United States around a central island and in which entering traffic must yield to circulating 

traffic. Figure 1 illustrates the key characteristics of a modern roundabout in the United States 

which include a generally circular shape, yield control of entering traffic, and geometric 

curvature and features to induce desirable traffic speeds.(1) Splitter islands have multiple roles, 

which include separating entering and exiting traffic, deflecting and slowing entering traffic, and 

providing a pedestrian refuge. (Figure 1) 

The use of roundabouts as an intersection form has grown substantially over the past 15 to 20 

years. As of 2005, there were 1,035 known roundabouts in the United States. By 2013, that 

number had been estimated to increase to over 3,200.(2) 

Past research has demonstrated a very low frequency of fatalities at roundabouts, but the research 

has not focused on the contributing factors of these fatalities and injuries. The information 

summarized in this report focuses on crash characteristics and first harmful event, as cited in 

available crash reports, to determine whether there are elements of roundabout design practice 

that can be modified to reduce the likelihood of a fatality or severe injury even further. This 

report covers the analysis of fatal crashes known to the team through December 2013. 

Figure 1. Diagram. Key characteristics of modern roundabouts. 

1 
 

 

The report addresses the following: 

• Provides an overview of crash trends from fatal crashes at all types of intersections across 

the United States and corresponding crash trends from the Washington and Wisconsin 

Strategic Highway Safety Plans to provide potential benchmarks for comparing crashes at 

roundabouts. 

• Summarizes the fatal crash review across the U.S. 

• Summarizes injury crashes at roundabouts in the States of Wisconsin and Washington. 

• Identifies key trends discovered in the analysis. 

• Recommends potential strategies to address fatal and injury crash characteristics. 

2 
 

 

 

 

 

 

 

 

 

 

 

CHAPTER 2. NATIONAL AND STATE CRASH BENCHMARKS 

National and state level benchmarks are useful points of reference to contrast the crash 

experience at roundabouts to other intersections and gauge whether or not there is a significant 

difference that could reveal an opportunity to improve safety through design modifications of 

roundabouts. 

The research team obtained crash history statistics and information from the Fatality Analysis 

Reporting System (FARS) maintained by the National Highway Traffic Safety Administration 

(NHTSA) and Strategic Highway Safety Plans (SHSPs) produced by the States of Washington 

and Wisconsin. These States have been recognized for many years as leaders in roundabout 

implementation and have large numbers of roundabouts as compared to most other States. With 

this information, the research team examined the prevalence of the following crash factors or 

characteristics at the national and statewide levels: intersections, alcohol-involved, speed-related, 

time of day, fixed object involved, motorcycle-involved, bicycle-involved and pedestrianinvolved. 

FATAL CRASH BENCHMARKS 

Fatal crash benchmarks were summarized for all fatal crashes in the United States as well as for 

the States of Washington and Wisconsin using the Fatality Analysis Reporting System (FARS) 

2012 data.(3) Table 1 summarizes the number of fatalities in the United States as well as the 

States of Washington and Wisconsin in 2012. Table 1 also summarizes the number of fatalities 

that occurred at intersections in each location. Twenty-six percent of all fatalities in the United 

States occurred at intersections. In Washington and Wisconsin, 23 percent and 27 percent of all 

fatal crashes, respectively, occurred at intersections. 

Table 1. Number of Fatalities in the United States in 2012. 

Total 

Number 

of 

Fatalities 

in the 

U.S. 

Number of 

Fatalities at 

Intersections 

in the U.S. 

(Percent of All 

Fatalities) 

Total 

Number of 

Fatalities in 

the State of 

Washington 

Number of 

Fatalities at 

Intersections 

in the State of 

Washington 

(Percent of All 

Fatalities) 

Total 

Number of 

Fatalities 

in the State 

of 

Wisconsin 

Number of 

Fatalities at 

Intersections 

in the State of 

Wisconsin 

(Percent of All 

Fatalities) 

33,782 8,851 

(26) 

438 101 

(23) 

615 169 

(27) 

Table 2 summarizes the characteristics of all fatal crashes as well as fatal crashes at intersections. 

The summary of characteristics of fatal crashes at intersections serves as a benchmark for 

comparisons with characteristics of fatal crashes at roundabouts. The data summarized in Table 2 

3 
 

 

are comprehensive of all fatal crashes and includes fatal crashes that occurred at roundabouts. 

However, the number of fatal crashes at non-roundabout intersections is much larger than the 

number of fatal crashes at roundabouts, allowing this data to serve as a useful comparison. 

4 
 

Table 2. Summary of fatal crash characteristics.(3) 

Crash 

Characteristic 

Number of 

Fatal Crashes 

in the U.S. 

(Percent of All 

Fatal Crashes 

with 

Characteristic) 

Number of Fatal 

Crashes at 

Intersections in 

the U.S. 

(Percent of All 

Fatal 

Intersection 

Crashes with 

Characteristic) 

Number of 

Fatal Crashes 

in Washington 

(Percent of All 

Fatal Crashes 

with 

Characteristic) 

Number of Fatal 

Crashes at 

Intersections in 

Washington 

(Percent of All 

Fatal 

Intersection 

Crashes with 

Characteristic) 

Number of 

Fatal Crashes 

in Wisconsin 

(Percent of All 

Fatal Crashes 

with 

Characteristic) 

Number of Fatal 

Crashes at 

Intersections in 

Wisconsin 

(Percent of All 

Fatal 

Intersection 

Crashes with 

Characteristic) 

Alcoholinvolved 

(Police 10,553 1,900 158 28 229 44 

Reported 

and/or (31) (21) (36) (28) (37) (26) 

BAC≥0.01) 

Speedingrelated (NonInterstate) 

8,689 

(26) 

1,789 

(20) 

137 

(31) 

28 

(28) 

192 

(31) 

38 

(22) 

Light 

Condition 

(Non-Daylight) 

17,443 

(52) 

3,792 

(43) 

228 

(52) 

38 

(38) 

275 

(45) 

63 

(37) 

Fixed Objects* 

10,995 

(33) 

937 

(11) 

132 

(30) 

17 

(17) 

225 

(37) 

28 

(17) 

5 
Crash 

Characteristic 

Number of 

Fatal Crashes 

in the U.S. 

(Percent of All 

Fatal Crashes 

with 

Characteristic) 

Number of Fatal 

Crashes at 

Intersections in 

the U.S. 

(Percent of All 

Fatal 

Intersection 

Crashes with 

Characteristic) 

Number of 

Fatal Crashes 

in Washington 

(Percent of All 

Fatal Crashes 

with 

Characteristic) 

Number of Fatal 

Crashes at 

Intersections in 

Washington 

(Percent of All 

Fatal 

Intersection 

Crashes with 

Characteristic) 

Number of 

Fatal Crashes 

in Wisconsin 

(Percent of All 

Fatal Crashes 

with 

Characteristic) 

Number of Fatal 

Crashes at 

Intersections in 

Wisconsin 

(Percent of All 

Fatal 

Intersection 

Crashes with 

Characteristic) 

Pedestrian 

4,679 

(14) 

1,416 

(16) 

70 

(16) 

22 

(22) 

39 

(6) 

13 

(8) 

Bicyclist 

736 

(2) 

310 

(4) 

14 

(3) 

8 

(8) 

10 

(2) 

4 

(2) 

Motorcycle 

4,986 

(15) 

2,017 

(23) 

83 

(19) 

22 

(22) 

117 

(19) 

37 

(22) 

*Includes Pole/Post, Culvert/Curb/Ditch, Shrubbery/Tree, Guardrail/Barrier/Cushion/End, Embankment, Bridge, and Other/Unknown. 

6 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As Table 2 shows, the fatal crash statistics in Washington and Wisconsin are similar to the 

overall fatal crash statistics nationally with the exception of fatal crashes involving pedestrians. 

Fatal crashes in Wisconsin involving pedestrians accounted for only eight percent of all fatalities, 

while those for the state of Washington and the entire United States accounted for 22 percent and 

16 percent of all fatalities respectively. 

The research team conducted further review of the SHSPs for these two states to obtain 

additional insight on severe crashes, or those resulting in injury, in addition to the fatal crash 

trends. 

INJURY CRASH BENCHMARKS 

The Washington State and Wisconsin Strategic Highway Safety Plans were used to summarize 

benchmarks for all injury crashes within each state. The information summarized in this section 

were used as benchmarks to compare roundabout injury crash characteristics in each State. 

The Washington State SHSP reviewed for this study (dated December 13, 2013)(4) identifies a 

number of issues related to injury and fatal crashes. The plan is based on a three-tiered 

prioritization system, which groups crash factors based on the number of fatalities or serious 

injuries that occurred between 2009 and 2011 involving that factor. Relevant Priority Level One 

factors include Impaired Driver(s) Involved, Run-Off-the Road Involved, Speed Involved, and 

Intersection Related. Priority Level Two factors include Motorcyclists and Pedestrians involved. 

Priority Level Three factors include Bicyclists involved. With the exception of Run-Off-Road 

instead of the more specific Fixed Object Involved category, these are the same crash factors 

noted in the fatal crash characteristics summarized in Table 2. Washington State has chosen a 

goal of “Target Zero” and is tracking progress toward zero fatalities by 2030. 

The Wisconsin SHSP (dated September 2014)(5) identifies many of the same issues cited above. 

The Wisconsin SHSP identifies the state’s 10 Highest Priority Areas, which include Improve 

Design and Operation of Intersections, Reduce Speed-Related Crashes, Prevent/Mitigate 

Roadway Departure Crashes, Provide Safe Pedestrian and Bicycle Travel, Reduce Alcohol/Drug 

Impaired Driving, and Improve Motorcycle Safety, among others. In the SHSP, Wisconsin sets a 

goal to reduce the number of fatal and incapacitating injury intersection crashes by 5 percent by 

2016. 

Table 3 summarizes the percentage of serious injuries associated with different crash 

characteristics. These statistics reflect the percentage of injuries rather than the percentage of 

crashes. Therefore, the statistics may not be used as a direct comparison with the number of 

crashes since a single crash may result in multiple injuries. The statistics show similar trends in 

both states among injury crashes. The percentage of serious injuries resulting from intersection 

crashes ranged from 34 percent in Washington to 39 percent in Wisconsin. The remainder of the 

trends shown in the table reflects trends from all serious injuries in the State, including those that 

occurred at both intersections and on roadway segments. Motorcycles were involved in 16 to 17 

percent of serious injuries, and impaired driving was involved in 17 to 21 percent of serious 

injuries. High speeds were involved in 27 to 29 percent of serious injuries, but it is unknown 

what percentage of these occurred at intersections. The largest difference in the trends between 

the two States was seen in the pedestrian and bicycle crashes. Seventeen percent of serious 

7 
 

 

 

injuries in Washington were associated with pedestrian and bicycle crashes, while only nine 

percent were pedestrian- or bicycle-related in Wisconsin. 

Table 3. Percentage of serious injuries by State by crash factor. 

Serious Injury Crash 

Factors Washington (2009 – 2011) Wisconsin (2008 – 2012) 

Intersections 34 39 

Motorcycles 17 16 

Impaired Driving 21 17 

Speeding & Speed-related 29 27 

Pedestrians & Bicycles 17 9 

The information summarized in Table 2 and Table 3 was used in Chapter 3 as benchmarks to 

compare the crash experience at roundabouts to national and statewide trends. 

8 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER 3. CRASH HISTORY REVIEW 

This chapter presents a review of all known fatal crashes and a sample of injury crashes that 

occurred at roundabouts in the United States. The review of all known fatal crashes was 

supplemented with a review of a sample of injury crashes to increase the sample size and identify 

more robust trends in crash history. 

FATAL CRASH REVIEW 

Fatal Crash Data 

The research team identified fatal crashes at roundabouts by searching through crash history data 

from the late 1990s to 2013. Methods of identifying crashes included FARS queries, soliciting 

and collecting information from the Roundabouts Listserv hosted by Kansas State University, 

internet search engines, professional contacts, personal experience and word of mouth. The first 

documented instance of a fatal crash at a roundabout in the United States occurred in the year 

2001. During the early 2000s, when roundabouts were relatively new in the United States, 

consistent terminology regarding roundabouts was not established. Crash reports and media 

coverage used the terms roundabouts, traffic circles, rotaries, circular intersections, “goarounds”, and others interchangeably, despite the differences in each intersection type. The 

essential characteristics of roundabouts (circulating priority, entry yield control, deflection at 

entry, low speed, etc.) were not fully understood by those completing the reports. These 

discrepancies in reporting still occur, although at a smaller scale, today. 

In addition to inconsistent reporting, the relative infrequency of fatal crashes at roundabouts 

makes capturing a comprehensive and verified list of all fatalities at roundabouts challenging. 

While the research team believes the effort to identify and verify the conditions and 

circumstances of crashes was thorough and appropriate, it is possible that other roundabout fatal 

crashes went unidentified because of the stated difficulties. If any fatal crashes were not 

identified, the number is expected to be small. The challenges of developing an accurate and 

comprehensive dataset of crashes at roundabouts demonstrates the need to improve crash 

reporting related to roundabouts to make this information more readily identifiable. 

Beginning with the first known and documented roundabout fatality in 2001, the research team 

verified 47 fatal crashes at roundabouts through 2013, with no fatal crashes found in years 2002, 

2003 and 2004. Roundabouts were relatively new in the United States prior to 2005; only 391 

known roundabouts existed in the United States in 2001. By 2005, the number of known 

roundabouts had reached 1035, and by 2013, over 3,200 roundabouts are believed to exist in the 

United States. (2) Therefore, the analysis time period for this study was limited to 2005 through 

2013, when roundabouts had become a well-established practice in several states and were 

increasing in numbers across the Country. Within the 2005 through 2013 study period, a total of 

46 fatal crashes were known to have occurred at roundabouts and are presented for analysis in 

this chapter. 

9 
 

 

 

 

 

 

Characteristics of Fatal Crashes at Roundabouts 

The crash reports and other information collected for the identified fatal crashes were reviewed 

and analyzed by the research team. The 46 fatal crashes at roundabouts occurred in 19 different 

States. As shown in Figure 2, there has been a general increasing trend in the number of fatal 

crashes at roundabouts per year starting in 2009, with the exception of 2013. Although the 

number of roundabouts in the United States has been increasing each year as shown in 

Figure 3, there has been a general increasing trend in the rate of fatal crashes per number of 

roundabouts in the United States over the past five years, as shown in Figure 4. 

14 

12 

10 

8 

6 

4 

2 

0 

Number of Fatal Crashes at

Roundabouts in the U.S. 

2005 2006 2007 2008 2009 2010 2011 2012 2013 

Figure 2. Chart. Number of Fatal Crashes at Roundabouts in the U.S. by Year. 

10 
 

3500 

3000 

2500 

2000 

1500 

1000 

500 

0 

2005 2006 2007 2008 2009 2010 2011 2012 2013 

Figure 3. Chart. Estimated Number of Roundabouts in the U.S. by Year. 

0.0045 

0.0040 

0.0035 

0.0030 

0.0025 

0.0020 

0.0015 

0.0010 

0.0005 

0.0000 

2005 2006 2007 2008 2009 2010 2011 2012 2013 

Figure 4. Chart. Estimated Number of Fatal Crashes per Roundabout in the U.S. by Year. 

The statistics summarized in Table 2 in Chapter 2 were specifically examined to compare the 

overall experience in the roundabout fatal crashes to national and statewide levels. Table 4 

summarizes the characteristics of the fatal crashes at roundabouts and compares them to the 

statistics of characteristics at all fatal crashes at intersections. Compared to fatal crashes at all 

intersections, fatal crashes at roundabouts had higher percentages of crashes that occurred during Number of Fatal Crashes per Estimated Number of Roundabout in the U.S. Roundabouts in the U.S. 

11 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

dark light conditions and crashes that involved motorcycles, speeding, impaired driving, and 

fixed objects. A high percentage (83 percent) of fatal roundabout crashes were single-vehicle 

crashes. 

Of the 24 impaired driving crashes, the majority (21 crashes) were associated with alcohol 

impairment, with the remainder due to medical or drug impairment. Of the 26 speed-involved 

crashes, at least two involved vehicles exceeding 100 miles per hour (mph). Many of the 

motorcycle crashes at roundabouts involved loss of control and motorcycles striking curbs. Many 

of the fixed object crashes involved vehicles striking the splitter and central islands of 

roundabouts, striking curbs and sometimes other fixed objects such as sign posts, light poles, 

landscaping walls, boulders, and trees. At least 35 of the 39 fixed object crashes involved 

vehicles striking a curb. Fatal roundabout crashes were less likely to involve pedestrians or 

bicyclists when compared to fatal intersection crashes. 

Table 4. Summary of characteristics of fatal crashes at roundabouts in the United States. 

Characteristics 

cited in Crash 

Reports 

Number of Crashes 

with Characteristic 

(Percent of all fatal 

roundabout crashes) 

Number of Crashes 

without Characteristic 

or where Information 

Not Reported 

(Percent of all fatal 

roundabout crashes) 

Percent of Fatal 

Crashes at All 

Intersections in 

the U.S. with 

Characteristic 

Multiple Vehicles 

Involved 8 (17) 38 (83) 67 

Vehicle Struck 

Fixed Object(s) 39 (85) 7 (15) 11 

Motorcycle 

Involved 21 (46) 25 (54) 23 

Speed Cited 26 (57) 20 (43) 20 

Impaired Driving 

Cited 24 (52) 22 (48) 21 

Bicyclist Involved 1 (2) 45 (98) 4 

Pedestrian 

Involved 0 (0) 46 (100) 16 

Light Conditions 

(Daylight) 20 (43) 26 (57) 57 

Multilane 

Roundabout 13 (28) 33 (72) N/A 

Due to the relatively small number of fatal crashes, the crash review was expanded to include an 

analysis of injury crashes in two states. The following section explains the trends identified 

among these crashes. 

12 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INJURY CRASH REVIEW 

The review of injury crashes was limited to reviewing crash data available from two states: 

Washington and Wisconsin, two states that are widely recognized as leaders in terms of the 

number of roundabouts. With higher numbers of roundabouts, these states’ experiences are 

valuable in identifying injury crash trends related to roundabouts to build upon information 

learned from the fatal crash review. 

The data analyzed includes injury crashes of all severity levels with a focus on serious injury 

crashes, which include those coded as A (incapacitating) and B (non-incapacitating) on the 

KABCO scale. Fatal crashes were excluded from the analysis. The states provided their crash 

data in the form of Excel databases to FHWA with permission to share the data with the research 

team. Crashes reviewed include crashes at roundabouts between 2001 and 2013, although the 

number of years included varies for each intersection based upon the opening date of the 

roundabout. 

Due to the larger datasets for injury data in each state, data review was limited to the crash 

records in Excel format. Without the crash report narratives, news stories, and physical 

information for each site, the detailed events of each crash could not be readily ascertained. 

Therefore, the data summarized in this section provides insight into common trends but cannot 

be used to provide details of crash causes and design elements that were identified in the fatal 

crash review. Some of these relationships may be inferred from the trends identified. 

Injury Crash Data 

Washington 

The database provided by the State of Washington included crashes occurring at neighborhood 

traffic circles in addition to roundabouts. To efficiently verify the validity of the data, crashes 

were geocoded using the intersection street names, highway names, and mileposts. After 

geocoding the crashes, each crash was given a control type to indicate whether the crash 

occurred at a roundabout that was included in an online database of roundabouts. Crashes that 

could not be verified as having occurred at a roundabout were excluded from analysis to avoid 

the inclusion of neighborhood traffic circles. 

The original dataset included 3,990 crash records, which included all levels of severity ranging 

from property-damage only to fatal crashes. The research team was unable to geocode 326 crash 

locations. In addition, 597 of the crash locations were at locations that were not identified as 

roundabouts. The majority of these locations were neighborhood traffic circles. Therefore, the 

analysis presented in this section is based on a dataset of 3,067 crashes of all severity levels at 

roundabouts. 

Wisconsin 

Wisconsin data for the injury analysis were from data used by the Traffic Operations and Safety 

(TOPS) Laboratory at the University of Wisconsin-Madison in a report completed in 2011. The 

data include information on crashes that occurred at 34 roundabouts in Wisconsin and do not 

include crashes from all roundabouts in the state. Data were provided in the format of one Excel 

13 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

file for each intersection. These files were used in a previous study that reviewed differences in 

crash patterns before and after construction of the roundabout. Each file included, at a minimum, 

a summary table indicating the number of crashes that occurred in the three years prior to the 

roundabout opening and the years immediately after the roundabout opening. The year that the 

roundabout opened was excluded from the data to account for change in conditions during and 

immediately after construction. 

Characteristics of Injury Crashes at Roundabouts 

Similar to the fatal crash analysis, injury crash data were reviewed for the two states to further 

examine crash trends that may lead to opportunities to modify design practices and potentially 

improve roundabout safety. Because crash records differ between states, slightly different data 

are recorded (and in different formats) for each state. Appendix B shows the graphs that support 

the trends discussed in this section, as well as other trends reviewed. Comparable graphs for each 

state are presented consecutively to reveal similar trends for both states. In some cases, 

comparable data were not available for both states, or the two datasets provided similar 

categories, although not exactly the same. 

In addition, the benchmarks summarized for each state in Chapter 2 cannot be used as a direct 

comparison to the crash statistics summarized in this section for two reasons: the benchmarks 

presented in Chapter 2 reflect the percentage of injuries rather than the percentage of crashes 

associated with a characteristic, and the benchmarks reflect percentages of all severe injuries in 

the state associated with a characteristic rather than only those injuries that occurred at 

intersections. 

The crash data for Washington included a total of 3,067 crashes. Of these, 2,465 (80 percent) did 

not result in an injury and were categorized as property-damage-only, as shown in figure 9. Of 

the 744 crashes in the roundabout database for Wisconsin, 599 (81 percent) were propertydamage only crashes, as shown in figure 10. For the purpose of this study, only crashes that 

resulted in an injury were included, with a focus on injury A (incapacitating injury) and B (nonincapacitating injury) crashes. Fatal crashes were excluded from the analysis because they were 

reviewed in the fatal crash analysis. 

For many trends, one figure is presented in Appendix B to show the trend among all injury 

crashes, and another figure is used to show the trend among the more severe crashes, those 

characterized as injury A and injury B. Characteristics among severe crashes sometimes differ 

from those of overall crashes. For the purpose of improving safety, highest priority will be given 

to addressing the most severe crashes. 

Table 5 summarizes the most common crash types among injury crashes at roundabouts in 

Washington and Wisconsin. In both states, rear-end crashes were the most common crash types 

among all injury crashes at roundabouts, but fixed object crashes were the most common crash 

types among the Injury A and B roundabout crashes. The most common objects struck at 

roundabouts were curbs, raised traffic islands, and raised median curbs. Crashes involving curbs 

were nearly 50 percent likely to involve impaired driving as a factor. 

14 
 

 

 

 

 

 

Table 5. Summary of crash type trends in injury crashes at roundabouts in Washington 

and Wisconsin. 

Crash 

Type 

Percentage of 

Injury A & B 

Crashes in 

Washington 

Percentage 

of All Injury 

Crashes in 

Washington 

Percentage of 

Injury A & B 

Crashes in 

Wisconsin 

Percentage 

of All Injury 

Crashes in 

Wisconsin 

Figures 

Illustrating 

Trend in 

Appendix B 

Fixed 

object 

crashes 

41 25 59 31 Figure 9 

Figure 10 

Rear-end 

Crashes 10 29 11 36 Figure 9 

Figure 10 

Table 6 shows that single-vehicle crashes and motorcycle crashes were common trends among 

the roundabout injury crashes. Single-vehicle crashes made up a higher proportion of the severe 

crashes as compared to all injury crashes. Impaired driving was more commonly reported in 

single-vehicle crashes than multiple vehicle crashes. Motorcycles were commonly involved in 

injury crashes at roundabouts and more likely to be severe crashes. Both motorcycles and nonmotorcycles were most likely to crash upon entering the roundabout, but motorcycles were more 

likely to crash while circulating the roundabout than non-motorcycles. At least half of severe 

motorcycle crashes were single-vehicle crashes. 

Pedestrians and bicyclists were involved in a small percentage of crashes, but they were more 

likely to be severe crashes, as shown in Table 6. Bicycles were more commonly involved in 

injury crashes at roundabouts than pedestrians. 

15 
 

 

 

 

 

Table 6. Summary of vehicle and participant type trends in injury crashes at roundabouts 

in Washington and Wisconsin. 

Vehicle or 

Participant 

Characteristic 

Percentage of 

Injury A & B 

Crashes in 

Washington 

Percentage 

of All Injury 

Crashes in 

Washington 

Percentage of 

Injury A & B 

Crashes in 

Wisconsin 

Percentage 

of All Injury 

Crashes in 

Wisconsin 

Figures 

Illustrating 

Trend in 

Appendix B 

Motorcycles 29 17 28 13 

Figure 23 

Figure 24 

Figure 25 

Figure 26 

Single-Vehicle 66 37 54 28 

Figure 31 

Figure 32 

Figure 33 

Figure 34 

Pedestrians 

Involved 3 2 0 0 

Figure 53 

Figure 54 

Figure 55 

Figure 56 

Bicyclists 

Involved 13 6 9 5 

Figure 53 

Figure 54 

Figure 55 

Figure 56 

Table 7 shows that impaired driving was more likely to be a factor in the severe crashes, 

accounting for 21 percent of severe crashes at roundabouts in Washington and 13 percent of 

severe crashes at roundabouts in Wisconsin. 

Table 7. Summary of injury crashes involving impaired driving at roundabouts in 

Washington and Wisconsin. 

Crash 

Factor 

Percentage of 

Injury A & B 

Crashes in 

Washington 

Percentage of 

All Injury 

Crashes in 

Washington 

Percentage of 

Injury A & B 

Crashes in 

Wisconsin 

Percentage 

of All Injury 

Crashes in 

Wisconsin 

Figures 

Illustrating 

Trend in 

Appendix B 

Impaired 

Driving 

Involved 

21 13 13 7 

Figure 27 

Figure 28 

Figure 29 

Figure 30 

Light conditions and inclement weather did not appear to be key factors in the injury crashes at 

roundabouts, as shown in Table 8 and Table 9. The majority of injury crashes occurred in 

daylight. Those crashes that did occur at night commonly occurred in locations with street lights, 

which are common design elements with roundabouts. Inclement weather did not appear to be a 

factor in the majority of crashes. 

16 
Table 8. Summary of light conditions in injury crashes at roundabouts in Washington and 

Wisconsin. 

Light 

Condition 

Percentage of 

Injury A & B 

Crashes in 

Washington 

Percentage of 

All Injury 

Crashes in 

Washington 

Percentage of 

Injury A & B 

Crashes in 

Wisconsin 

Percentage 

of All Injury 

Crashes in 

Wisconsin 

Figures 

Illustrating 

Trend in 

Appendix B 

Dark, With 

Lights 31 35 15 21 

Figure 19 

Figure 20 

Figure 21 

Figure 22 

Dark, No 

Lights 2 2 4 2 

Figure 19 

Figure 20 

Figure 21 

Figure 22 

Table 9. Summary of weather conditions in injury crashes at roundabouts in Washington 

and Wisconsin. 

Weather 

Condition 

Percentage of 

Injury A & B 

Crashes in 

Washington 

Percentage of 

All Injury 

Crashes in 

Washington 

Percentage of 

Injury A & B 

Crashes in 

Wisconsin 

Percentage 

of All Injury 

Crashes in 

Wisconsin 

Figures 

Illustrating 

Trend in 

Appendix B 

Clear or 

partly cloudy 71 69 54 57 

Figure 15 

Figure 16 

Figure 17 

Figure 18 

Overcast 16 15 30 31 

Figure 15 

Figure 16 

Figure 17 

Figure 18 

Rain, snow, 

or other 14 16 17 12 

Figure 15 

Figure 16 

Figure 17 

Figure 18 

17 
 

 

SUMMARY OF CRASH TRENDS 

This review of fatal and injury crashes revealed several similar trends. Many of these were 

similar to general trends seen at the state and national level, implying that they may not be 

specific to roundabouts. Other trends indicate factors at roundabouts that may be considered for 

modifications to current design practices. 

Major Trends 

As shown in Figure 5, the majority of fatal roundabout crashes were single-vehicle crashes. For 

severe injury crashes at roundabouts in Washington and Wisconsin, multiple vehicle crashes 

were more common, but single-vehicle crashes still accounted for over half of all roundabout 

crashes in each state. 

Figure 5. Chart. Percent of crashes that were single-vehicle crashes. 

A relatively high percentage of crashes at roundabouts involved motorcycles. Nationally, the 

number of crashes involving motorcycles has been increasing in recent years. In 2012, 

motorcycles were involved in 23 percent of all traffic fatalities at intersections nationally. Figure 

6 shows that the percentage of injury A and B crashes in Washington and Wisconsin that 

involved motorcycles was 29 percent and 28 percent, respectively, and 46 percent of fatal 

crashes involved motorcycles. 

18 
 

 

Figure 6. Chart. Percent of crashes involving motorcycles. 

Many injury and fatal crashes at roundabouts involved impaired driving, as shown in Figure 7. 

This is a common trend nationally, as 21 percent of all traffic fatalities at intersections in 2012 

involved an alcohol-impaired driver. However, this statistic is even higher for roundabouts, 

where alcohol-impaired drivers were involved in percent of all fatal crashes. 

19 
 

 

 

 

Figure 7. Chart. Percent of crashes involving impaired driving. 

Fixed-object crashes, including crashes involving vehicles that hit the curb, were the most 

common fatal and severe injury crash type. As shown in Figure 8, many crashes involved 

vehicles losing control after hitting the curb, especially the back edge of the truck apron. Curbs 

are an important element in roundabout design. However, the design of the back edge of the 

truck apron may benefit from modification to reduce the likelihood of roll-overs after vehicles 

strike the curb. 

20 
 

 

 

 

 

 

 

 

 

 

 

Figure 8. Chart. Percent of crashes involving vehicles hitting the curb. 

Traveling at high speeds was a common contributing factor in the fatal crash reports. Speed was 

cited in 20 percent of fatal crashes at intersections in the U.S. in 2012, but speed was involved in 

at least 57 percent of fatal roundabout crashes. 

Summary 

Based on the trends identified in the fatal and injury crash review, several potential opportunities 

to improve safety at roundabouts were identified. The factors identified related to roundabout 

design, including curb design and placement of fixed objects, factors related to motorcycle 

crashes, and factors related to intersection awareness and driver education and enforcement. 

Engineering, which includes roadway design, is one component that may impact safety at 

roundabouts. Curbs are important at roundabouts to control speeds, but the frequency of fatal 

crashes involving the back edge of the truck apron may indicate the need for a central island 

curbing design modification. Consideration of the placement of fixed objects relative to 

roundabouts may also reduce risk. However, some fixed objects are necessary: curbs to manage 

entry speed; sign posts to provide regulatory and wayfinding guidance; and street light poles to 

provide lighting at the roundabout. 

Another common factor was motorcycle crashes. Research pertaining to roadway design to 

improve the safety for motorcyclists is limited. Some international research suggests that 

pavement treatments, entry radius at roundabouts, roadway barrier design, and fixed object 

placement may be considerations for accommodating motorcyclists. However, these have not 

been adequately tested through in-depth research studies to date. 

21 
 

 

The high number of crashes involving dark conditions, speeding, and single-vehicle crashes may 

indicate that drivers were unaware of approaching the roundabouts, making intersection 

awareness another factor, similar to other types of intersection control. A review and 

consideration of intersection awareness at roundabouts may be needed to determine whether 

opportunities exist to improve intersection awareness at roundabouts. 

Many of these crashes also involved impaired drivers, and driver education and enforcement 

could be another factor to help reduce crashes. 

Chapter 4 summarizes the recommendations that result from the findings of this study. 

22 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER 4. CONCLUSIONS AND RECOMMENDATIONS 

Prior research has confirmed that severe crashes, defined as crashes that result in injury or 

fatality, are less frequent at roundabouts than at conventional signalized and stop-controlled 

intersections. However, as this study has documented, some fatal and injury crashes have 

occurred at roundabouts. Crash characteristics and trends identified from fatal roundabout 

crashes throughout the United States over an extended time period, and multiple years of injury 

crashes from roundabouts in the states of Washington and Wisconsin, provide useful insights for 

both the road design and traffic safety communities. These insights have informed four 

categories of recommendations based on overarching themes, as follows: recommendations 

addressing fixed object crashes at roundabouts; recommendations addressing motorcycle crashes 

at roundabouts; recommendations addressing intersection visibility and conspicuity at 

roundabouts, and education and enforcement strategies to complement engineering 

recommendations. These categories capture concepts from the first three of the “Four E’s” of 

traffic safety: engineering, enforcement, education, and emergency response. 

FIXED OBJECTS 

Fixed-object crash types were the most common crash types among the Injury A and B crashes at 

roundabouts in Washington and Wisconsin and were involved in 85 percent of fatal crashes at 

roundabouts. Of the 39 fatal fixed object crashes at roundabouts, 35 involved vehicles striking 

the curb. In some cases, multiple fixed objects were involved in a single crash. For example, a 

vehicle may have struck the curb first and a sign post second. 

Given that roundabouts rely on effective channelization using raised features such as splitter 

islands and central islands, as well as on signing to communicate legal movements and right-ofway to users, some fixed objects are inherent in the design of roundabouts and must be present in 

the design. Other objects that were hit, such as boulders, retaining walls, trees, and landscaping, 

may be optional at many roundabout locations. Based on these observations, the following 

sections summarize recommendations made about fixed objects. 

Curbs 

Curbs were frequently involved in the roundabout injury and fatal crashes, and in some cases, 

were related to subsequent harmful events. Past research on curbs and their relationship to 

roadside safety hardware (NCHRP Report 537) demonstrates how varying curb characteristics 

produce different vehicle responses, including temporary loss of control and even overturn at 

higher speeds.(6) Since curbs are an essential component of roundabouts for the channelization 

features and functional delineation features, it is not practical to omit curbs as a roundabout 

design component. Splitter islands’ function is to provide refuge for pedestrians, help control 

entry speeds, guide vehicles into the roundabout, and provide physical separation for entering 

and existing vehicles. Raised central islands are provided to enhance driver awareness of the 

approaching roundabout. (1) 

Agencies and designers should review what curb types are presently used at roundabouts in their 

jurisdictions and consider if other curb types are available or if modifications may be made that 

would retain the basic advantages and functions, while reducing the potential for adverse effects. 

23 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Generally, types of curbs that feature milder sloping faces and/or less vertical height or reveal 

can still provide a raised channelization or delineation effect, with less potential for inducing 

vehicle instability. Curbs with milder sloping faces and less vertical height or reveal have also 

been shown to be more accommodating to a wider range of truck/freight combinations (i.e., lowclearance and/or oversize). 

Rigid Fixed Objects 

Thoughtful placement of fixed objects is a basic principle of proper roadside design. In 2011, the 

American Association of State Highway and Transportation Officials (AASHTO) published an 

updated Roadside Design Guide (RDG), and the revisions to Chapter 10 on Roadside Safety in 

Urban or Restricted Environments represented a new perspective on roadside design in lower 

speed and urban contexts.(7) Roundabouts share many of the characteristics discussed in this 

chapter of the RDG, and hence the updated guidance may be of value for roundabout design as 

well. In particular, as described in the RDG, it could be worthwhile to consider what may be 

“high risk” locations for fixed objects unique to roundabouts, given the movements of traffic 

approaching, circulating, and leaving the vicinity of a roundabout. 

MOTORCYCLES 

Motorcycles are overrepresented in severe crashes at roundabouts as compared to national and 

statewide trends for intersections. Addressing curbs as indicated above would likely have a 

positive effect for motorcycles because milder sloped curbs could reduce the adverse effects of a 

motorcycle impact. In addition, the evaluation of fixed object placement to minimize potential 

points of impact would be beneficial to motorcycles. 

While wet pavement was not a significant factor identified by this analysis, it is possible that 

pavement-tire friction could play a role in some motorcycle crashes. Therefore, another possible 

mitigation strategy to consider for motorcycles and other vehicles is the documented practice 

from the United Kingdom to apply high friction surface treatments to roundabouts. Federal 

Highways Administration research has shown that high-friction surfaces have been successful in 

reducing crashes at intersections with curvature, frequent wet pavement, and steep grades.(8) 

These results indicate that high-friction surfaces may have applications at roundabouts. Further 

tests may be needed to determine how motorcycles perform on these surfaces before widespread 

implementation. 

VISIBILITY AND CONSPICUITY 

Dark lighting conditions, high speeds, and single-vehicle crashes were also common themes in 

the fatal and injury roundabout crashes. These trends may suggest that the drivers who were 

approaching the roundabout were unaware of the upcoming roundabout. Therefore, intersection 

visibility and conspicuity is another design factor that should be considered at roundabouts, 

particularly those in more rural locations. 

As discussed in NCHRP Report 672, additional advanced illumination and changes to the 

roadway environment such as extending the length of splitter islands on approaches may better 

inform the driver of the approaching roundabout. Pavement markings and adequate advanced 

warning signage may also be used to inform drivers of the upcoming roundabout. 

24 
 

 

 

 

 

 

 

 

EDUCATION AND ENFORCEMENT 

Many of the fatal and injury crashes at roundabouts involved impaired drivers and excessive 

speeds. Although roadway design is an important role in roadway safety, education and 

enforcement should be used in conjunction with engineering to obtain the most effective use of 

resources. Enhanced enforcement may be used to encourage drivers to follow the posted speed 

limit. Enforcement may also help keep impaired drivers off the road. Educating drivers of the 

proper method of driving roundabouts and the proper design speed of roundabouts may 

encourage them to slow down when approaching a roundabout. 

ADDITIONAL RECOMMENDATIONS 

The findings of this study were based on crash data from crashes that occurred at roundabouts. 

One of the challenges documented in Chapter 3 was the difficulty in verifying that crashes 

occurred at modern roundabouts rather than traffic circles or other intersection forms. Programs 

to educate all law enforcement staff and others who are responsible for completing crash reports 

about the unique characteristics of modern roundabouts would also help lead to a more accurate 

and comprehensive dataset of crashes at roundabouts to make information more readily 

identifiable in the future. Readily available data will enable future analysis and monitoring of 

safety trends at roundabouts to determine if design changes have impacts on safety trends. 

25 

 

REFERENCES 

1. Rodegerdts, L., J. Bansen, C. Tiesler, J. Knudsen, E. Myers, M. Johnson, M. Moule, B. 

Persaud, C. Lyon, S. Hallmark, H. Isebrands, R. B. Crown, B. Guichet, and A. O’Brien. 

NCHRP Report 672: Roundabouts: An Informational Guide, 2nd ed. Transportation 

Research Board of the National Academies, Washington, D.C., 2010. 

2. Rodegerdts, L. “Status of Roundabouts in North America.” Presented at TRB 4th 

International Conference on Roundabouts, Seattle, Washington, April 2014. 

3. Fatality Analysis Reporting System (FARS). National Highway Traffic Safety 

Administration. 

4. Washington Traffic Safety Commission. Washington State Strategic Highway Safety Plan 

2013. http://www.wsdot.wa.gov/NR/rdonlyres/5FC5452D-8217-4F20-B2A9-

080593625C99/0/TargetZeroPlan.pdf. 

5. Wisconsin Department of Transportation. Wisconsin Strategic Highway Safety Plan 2014 – 

2016. September 2014. http://www.dot.wisconsin.gov/library/publications/topic/safety/hwystrategic-safety-plan.pdf. 

6. Plaxico, C. A., M. H. Ray, J. A. Weir, F. Orengo, P. Tiso, H. McGee, F. Council, and K. 

Eccles. NCHRP Report 537: Recommended Guidelines for Curb and Curb-Barrier 

Installations. Transportation Research Board. Washington, DC, 2005. 

7. American Association of State Highway and Transportation Officials (AASHTO). Roadside 

Design Guide. AASHTO, Washington, D.C., 2011. 

8. Julian, F. and S. Moler. “Gaining Traction in Roadway Safety.” Public Roads. Federal 

Highway Administration. http://www.fhwa.dot.gov/publications/publicroads/08july/05.cfm 

27 

 

 

 

 

 

 

 

 

 

 

 

 

 

APPENDIX A. FATAL CRASH DATA 

Table 10. Fatal crash data. 

# Year Month Date Time State City Intersection Type Conditions Lighting Vehicles Vehicle 

Type(s) 

Speed 

Cited 

Impaired 

Cited 

Fixed 

Object(s) 

Cited 

1 2005 Jan 28 1:34 FL Del Ray 

Beach 

Lake Ida 

Rd./Via Flora Single Clear, Dry DarkLighted 1 Motorcycle Yes No Curb 

2 2005 Oct 30 1:52 WI Howard Lineville 

Rd./Yelp Ave. Single Clear, Dry DarkLighted 1 Motorcycle NR Yes Curb, Sign 

3 2006 Apr 2 7:43 KS Wichita Sycamore St./ 

Douglas Ave. Single Clear, Dry Daylight 1 Car No No 

Curb, Object 

in Central 

Island 

4 2006 Aug 12 1:37 WA Tacoma S. Tyler St./S. 

66th St. Single Clear, Dry DarkLighted 2 Motorcycle, Car Yes No NR 

5 2007 Feb 22 0:44 CO Avon US 6/Post 

Blvd. Multi Clear, Dry DarkLighted 1 Car Yes Yes Curb, Light Pole 

6 2007 Mar 4 17:4 

0 KS Lawrence 

Clinton 

Pkwy./Lake 

Pointe Dr. 

Single Clear, 

Debris Daylight 1 Motorcycle NR No Curb 

7 2007 Jun 5 15:2 

0 NC Waynesville 

US 23B/ 

Ratcliffe Cove 

Rd./Zemery 

Ln. 

Single Clear, Dry Daylight 1 Car No No Tree 

8 2007 Oct 1 3:10 IN Carmel 

N. Westfield 

Blvd./E. 96th 

St. 

Single Clear, Dry DarkLighted 1 Car Yes No 

Curb, Wall in 

Central 

Island 

9 2007 Oct 7 2:30 CA Encinitas 

Santa Fe Dr./ 

Rubenstein 

Ave./Devonshi 

re Rd. 

Single Clear, Dry DarkLighted 1 Pickup Yes Yes Curb, Light 

Pole 

10 2007 Oct 14 17:1 

8 MD Burtonsville 

US 29 SB 

Ramps/Dustin 

Rd./Columbia 

Pike 

Single Clear, Dry Daylight 1 Car Yes Yes 

Curb, 

Roadside 

Wall 

11 2008 Mar 13 1:30 FL Punta Gorda Beach 

Rd./Gulf Blvd. Single Clear, Dry DarkLighted 1 Car Yes Yes Curb, Fence, Tree 

29 
 

 

 

 

 

 

 

 

 

 

 

 

 

# Year Month Date Time State City Intersection Type Conditions Lighting Vehicles Vehicle 

Type(s) 

Speed 

Cited 

Impaired 

Cited 

Fixed 

Object(s) 

Cited 

12 2008 May 14 23:1 

6 NC Charlotte 

Moore Chapel 

Rd./I-485 NB 

Ramps 

Single Clear, Dry 

Dark-

Not 

Lighted 

1 Car Yes Yes Curb 

13 2009 Jul 23 16:2 

3 KS Manhattan SR 18/Scenic Dr. Single Clear, Dry Daylight 2 Motorcycle, SUV No No None 

14 2009 Sep 15 2:11 CA Oxnard 

N. Ventura 

Rd./ Forest 

Park Blvd. 

Multi Clear, Dry Dark

-

Lighted 1 Motorcycle NR Yes Curb 

15 2009 Oct 15 15:2 

6 CA Santa Maria 

McCoy 

Ln./South 

College Dr. 

Single Clear, Dry Daylight 1 SUV Yes Yes Curb, Fence 

16 2010 Jan 20 21:0 

5 KS Macpherson N. Centennial Dr./E. First St. Single Cloudy/Fog , Dry 

Dark-

Lighted 1 Car Yes Yes Curb, Wall 

17 2010 Jan 31 12:2 

8 KS Manhattan 

Kimball 

Ave./Grand 

Mere Pkwy. 

Single Cloudy, Dry Daylight 1 Car No No Curb, Wall 

18 2010 Feb 21 1:25 FL Orlando Yucatan 

Dr./Oxalis Dr. Mini Clear, Dry Dark

-

Lighted 1 Motorcycle Yes No Curb, Parked Car 

19 2010 Apr 4 3:04 TN Chattanoog 

a 

SR 

153/Access 

Rd. 

Multi Clear, Dry Dark

-

Lighted 2 Motorcycle, 

Car Yes Yes None 

20 2010 Jul 10 20:3 

3 WI Delton 

Moon 

Rd./Timothy 

Ln. 

Multi Clear, Dry Daylight 1 Motorcycle Yes Yes 

Curb, 

Central 

Island, Sign 

Post 

21 2010 Oct 28 3:25 NV Summerlin 

W. Flamingo 

Rd./Granite 

Ridge Dr. 

Multi Clear, Dry Dark

-

Lighted 1 Motorcycle Yes Yes Curb 

22 2011 May 10 12:3 

7 MN New Prague TH 19/11th Ave. Single Windy, Cloudy, Dry Daylight 1 Motorcycle No No Curb, Sign, Tree 

23 2011 Jun 5 19:2 

7 WI Howard Woodale Ave./Velp Ave. Single Clear, Dry Daylight 1 Motorcycle No Yes Curb 

30 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

# Year Month Date Time State City Intersection Type Conditions Lighting Vehicles Vehicle 

Type(s) 

Speed 

Cited 

Impaired 

Cited 

Fixed 

Object(s) 

Cited 

24 2011 Jun 16 21:0 

3 FL Wildwood 

Buena Vista 

Blvd./Pinellas 

Pl. 

Multi Clear, Dry Dark

-

Lighted 2 Car, Golf Cart No No None 

25 2011 Jun 28 21:2 

0 NC Charlotte 

Moore Chapel 

Rd./I-485 NB 

Ramps 

Single Rain, Wet 

Dark-

Not 

Lighted 

1 Car No No Guardrail 

26 2011 Jun 29 16:5 

7 IN South Bend 

US 

20/Lexington 

Ave. 

Multi Clear, Dry Daylight 1 Car Yes No Curb, Pole 

27 2011 Oct 28 1:32 NY Hamburg US 62/Big 

Tree Rd. Single Clear, Dry Dark

-

Lighted 1 Car Yes Yes Curb, Boulders 

28 2011 Nov 24 19:4 

5 GA Douglasville SR 5/SR 166 Single Clear, Dry 

Dark-

Not 

Lighted 

1 Minivan NR NR Curb, Wall 

29 2011 Dec 22 21:0 

0 WA Mount Vernon 

SR 538/SR 9 Single NR Dark 2 Car (both) No Yes* 

Curb, Light 

Pole, Parked 

Car 

30 2012 Jan 1 16:3 

3 AZ Clarkdale SR 89A/Valley View Rd. Multi Cloudy, Dry Daylight 1 Motorcycle Yes Yes Curb 

31 2012 Jan 8 23:4 

0 WI Appleton US 10/CH N Single Clear, Dry Dark

-

Lighted 1 Car Yes Yes Curb 

32 2012 Jan 22 18:1 

0 FL Land O’Lakes 

Connerton 

Blvd./Park 

Bench Ct. 

Multi Clear, Dry Dark

-

Lighted 1 Motorcycle No Yes Curb 

33 2012 Jun 4 10:2 

6 MT Billings 

Shiloh 

Rd./Grand 

Ave. 

Multi Clear, Dry Daylight 2 Car, SUV No Yes* None 

34 2012 Jun 10 0:35 WI Marinette SR 64/CH T Single Clear, Dry Dark

-

Lighted 1 Car Yes Yes Boulder, Tree 

35 2012 Jun 10 19:5 

6 CA Ripon N. Ripon Rd./River Rd. Single Clear, Dry Daylight 1 Motorcycle Yes Yes Curb, Pole 

36 2012 Jun 20 20:4 

1 MI Clinton 

Cass 

Ave./Romeo 

Plank Rd. 

Multi Clear, Dry Daylight 1 Motorcycle No Yes* Curb 

31 
 

 

 

 

 

 

 

 

 

 

 

 

 

# Year Month Date Time State City Intersection Type Conditions Lighting Vehicles Vehicle 

Type(s) 

Speed 

Cited 

Impaired 

Cited 

Fixed 

Object(s) 

Cited 

37 2012 Jun 30 2:12 FL Fleming 

Island 

Town Center 

Blvd./EastWest Pkwy. Single Clear, Dry 

DarkNot 

Lighted 

1 Car Yes Yes Sign, Tree, 

Utility Pole 

38 2012 Aug 23 6:09 FL Jacksonville Huffman 

Blvd./Walle Dr. Single Clear, Dry Daylight 1 Motorcycle No No None 

39 2012 Nov 21 23:1 

5 LA Lafayette SR 93/SR 98 Single Clear, Dry 

DarkNot 

Lighted 

1 Motorcycle Yes NR Curb 

40 2012 Nov 24 14:5 

5 CA Truckee 

Donner Pass 

Rd./McIver 

Crossing/ 

Lincoln Hwy 

Single Clear, Dry Daylight 2 Bicycle, Car No No None 

41 2012 Dec 1 0:42 AZ Chino Valley SR 89/Outer 

Loop Rd. Multi Clear, Dry DarkLighted 1 Pickup Yes Yes Curb 

42 2013 May 1 12:1 

3 AZ Salome US 60/ Vicksburg Rd. Single Clear, Dry Daylight 2 Pickup, SemiTruck No No Curb, Sign, Vehicle 

43 2013 Aug 11 2:09 NY Hamburg US 62/Big 

Tree Rd. Single Clear, Dry DarkLighted 1 Motorcycle Yes Yes Curb 

44 2013 Aug 29 18:2 

2 WI New Berlin I-43 NB Ramps/CH Y Multi Clear, Dry Daylight 1 Motorcycle No Yes Curb 

45 2013 Sep 1 13:4 

3 OR Newberg 

N.Springbrook 

Rd./ 

E.Crestview 

Dr. 

Single Clear, Dry Daylight 1 Motorcycle Yes No Curb 

46 2013 Dec 10 1:16 FL Gainesville 

SW 24th 

Ave./SW 38th 

Terr. 

Single Cloudy, Dry DarkLighted 1 Car Yes Yes Curb, Sign, 

Tree 

32 
 

 

APPENDIX B: INJURY CRASH DATA TRENDS 

INJURY SEVERITY 

Figure 9. Chart. Number of crashes by injury severity, Washington; “PDO” stands for 

“property damage only.” 

Figure 10. Chart. Number of crashes by injury severity, Wisconsin. “PDO” stands for 

“property damage only.” 

33 
 

TIME OF DAY 

Figure 11. Chart. Time of day for all injury crashes, Washington. 

Figure 12. Chart. Time of day for injury A and B crashes, Washington. 

34 
Figure 13. Chart. Time of day for all injury crashes, Wisconsin. 

Figure 14. Chart. Time of day for injury A and B crashes, Wisconsin. 

35 
 

WEATHER 

Figure 15. Chart. Weather, all injury crashes, Washington. 

Figure 16. Chart. Weather, for injury A and B crashes, Washington. 

36 
 

 

Figure 17. Chart. Weather, for all injury crashes, Wisconsin. 

Figure 18. Chart. Weather, for injury A and B crashes, Wisconsin. 

37 
LIGHT CONDITIONS 

Figure 19. Chart. Light conditions for all injury crashes, Washington. 

Figure 20. Chart. Light conditions for injury A and B crashes, Washington. 

38 
Figure 21. Chart. Light conditions for all injury crashes, Wisconsin. 

Figure 22. Chart. Light conditions for injury A and B crashes, Wisconsin. 

39 
 

 

VEHICLE TYPE 

Figure 23. Chart. Vehicle type for all injury crashes, Washington. 

Figure 24. Chart. Vehicle type for all injury A and B crashes, Washington. 

40 
Figure 25. Chart. Vehicle type for all injury crashes, Wisconsin. 

Figure 26. Chart. Vehicle type for injury A and B crashes, Wisconsin. 

41 
ALCOHOL INVOLVEMENT 

Figure 27. Chart. Alcohol involvement for all injury crashes, Washington. 

Figure 28. Chart. Alcohol involvement in injury A and B crashes, Washington. 

42 
 

Figure 29. Chart. Alcohol involvement in all injury crashes, Wisconsin. 

Figure 30. Chart. Alcohol involvement in injury A and B crashes, Wisconsin. 

43 
NUMBER OF VEHICLES INVOLVED 

Figure 31. Chart. Number of vehicles involved, all injury crashes, Washington. 

Figure 32. Chart. Number of vehicles involved, injury A and B crashes, Washington. 

44 
Figure 33. Chart. Number of vehicles involved, all injury crashes, Wisconsin. 

Figure 34. Chart. Number of vehicles involved, injury A and B crashes, Wisconsin. 

45 
 

ALCOHOL INVOLVEMENT AND NUMBER OF VEHICLES INVOLVED 

Figure 35. Chart. Alcohol involvement and number of vehicles involved, all injury crashes, 

Washington. 

Figure 36. Chart. Alcohol involvement and number of vehicles involved, injury A and B 

crashes, Washington. 

46 
 

 

Figure 37. Chart. Alcohol involvement and number of vehicles involved, all injury crashes, 

Wisconsin. 

Figure 38. Chart. Alcohol involvement and number of vehicles involved, injury A and B 

crashes, Wisconsin. 

47 
 

 

NUMBER OF VEHICLES INVOLVED AND VEHICLE TYPE 

Figure 39. Chart. Number of vehicles involved and vehicle type, all injury crashes, 

Washington. 

Figure 40. Chart. Number of vehicles involved and vehicle type, injury A and B crashes, 

Washington. 

48 
 

 

Figure 41. Chart. Number of vehicles involved and vehicle type, all injury crashes, 

Wisconsin. 

Figure 42. Chart. Number of vehicles involved and vehicle type, Injury A and B crashes, 

Wisconsin. 

49 
CRASH TYPE 

Figure 43. Chart. Crash type for all injury crashes, Washington. 

Figure 44. Chart. Crash type for all Injury A and B crashes, Washington. 

50 
 

 

Figure 45. Chart. Crash type for all injury crashes, Wisconsin. 

Figure 46. Chart. Crash type for injury A and B crashes, Wisconsin. 

51 
 

 

OBJECTS STRUCK 

Figure 47. Chart. First and second objects struck, all injury crashes, Washington. 

Figure 48. Chart. First and second objects struck, injury A and B crashes, Washington. 

52 
CONTRIBUTING CIRCUMSTANCES 

Figure 49. Chart. Contributing circumstances for all injury crashes involving vehicles 

hitting the curb, Washington. 

Figure 50. Chart. Contributing circumstances for all injury A and B crashes involving 

vehicles hitting the curb, Washington. 

53 
JUNCTION RELATION BY VEHICLE TYPE 

Figure 51. Chart. Junction relation by vehicle type, all injury crashes, Washington. 

Figure 52. Chart. Junction relation by vehicle type, injury A and B crashes, Washington. 

54 
 

PEDESTRIAN AND BICYCLIST CRASHES 

Figure 53. Chart. Pedestrian and bicyclist crashes, all injury crashes, Washington. 

Figure 54. Chart. Pedestrian and bicyclist crashes, injury A and B crashes, Washington. 

55 
 

 

Figure 55. Chart. Pedestrian and bicyclist crashes, all injury crashes, Wisconsin. 

Figure 56. Chart. Pedestrian and bicyclist crashes, injury A and B crashes, Wisconsin. 

56 
PUBLICATION NO. FHWA-SA-15-072