Roundabouts: Why is Mn/DOT Building Them?

1. Roundabouts: Why is Mn/DOT Building Them? Traffic Topics August 5, 2010 Ken E. Johnson Mn/DOT Office of Traffic, Safety, and Technology Member of Mn/DOT Roundabout Steering Committee ken.johnson@state.mn.us 651-234-7386

2. Ken’s RA Biography • Experienced RAs in Ireland in 1999 & 2001 • The only intersection I didn’t need to think about • Roundabouts: It’s Time for Minnesota • Capstone project for Masters degree • Coauthored with John Gorder and Brian Malm • Member of Mn/DOT’s Roundabout Steering Committee and Roundabout Review Team

3. Introduction to Roundabouts • Why consider roundabouts? • What is a roundabout – what is a traffic circle? • What’s so great about them anyway? • Advantages and Goals • Location considerations • What’s happening at Mn/DOT? • How do we decide? • Changes to traffic control devices

4. Mn/DOT Strategic Directions • Safety • Mobility • Innovation • Leadership • Transparency The appropriate application of Roundabouts is in line with 3 of the Strategic Directions of the Department

5. Roundabouts are … • Not social engineering • Not the Europeanization of America • Not the solution for world peace • Merely one type of intersection control made of concrete, asphalt, gravel, dirt, etc. • One of the tools that traffic engineers use to control crossing traffic.

6. Intersection Controls • Why – because that’s where vehicles cross paths which leads to delay and the possibility of crashes • Types • Yield controlled • TWSC (Two way stop controlled) • AWSC (All way stop controlled) • Signalization • Roundabouts • Continuous flow intersections and other non-typical types

7. TWSC Intersections • Mn/DOT’s good old default • Mobility is our major goal • But what if there are problems… • Crashes • Side street traffic gets heavy enough that excessive delay occurs to the minor road traffic • AWSC – usually very safe, but bad for delay • Signals – can help with delay, but safety can be issue • Interchanges - $$$$$ • Roundabout – in appropriate application, very safe and has less delay than other intersection types

8. Introduction to Roundabouts The image that many American’s have… Unfortunate misconception Video courtesy of Mark Johnson, MTJ Engineering

9. Not Traffic Circles, Rotaries, etc. Modern roundabouts vs. traffic circles: • Yield on entry – first rule (UK 1966) • Counter-clockwise circulation • Lower speeds necessary - deflection • Splitter islands • Central island • Pedestrian movements restricted to crossing legs • No parking First RB in USA – Summerlin, NV early ‘90s

10. Roundabout Features Roundabouts: An Informational Guide – FHWA, Exhibit 1-2

11. Introduction to Roundabouts This is an example of a modern roundabout…

12. Types of Roundabouts and Typical Volumes Assuming 4 perpendicular legs with balanced flows In general, can handle similar volumes as signals that are not failing

13. Rough Entering Volumes

14. That much traffic? Signal – 4,400 vph Loveland, CO Roundabout - 4,000 vph Avon, CO Video courtesy of Bill Hange, City of Loveland and Mark T. Johnson, MTJ Engineering Video courtesy of Leif Ourston, Ourston Roundabout Engineering

15. Advantages – Reduced Delay • Delay is the difference between • Travel time with no intersection control • Travel time with intersection control • Includes slow down, stop, and speed up time • Always better than AWSC • Usually better than TWSC if minor road volumes are close to major road volumes • 50/50, 60/40, 70/30 • Usually better than signal

16. Delay Reduction - Signalized “Average delay per vehicle at the MUTCD peak hour signal warrant thresholds” for various volumes Roundabouts: An Informational Guide – FHWA, Exhibit 3-7

17. Advantages – Increased Safety Reduced conflict points (8 vs. 32) Roundabouts: An Informational Guide – FHWA, Exhibit 2-3

18. Advantages • Increased safety (continued) • Shallow angle of conflict • Slower speeds • Better reaction time • Reduced severity of crashes • Energy = ½ x mass x speed x speed • Simplified decision making • Right turn at residential T-intersection

19. Simple decision – Wait for opening(right turn at residential T-intersection)

20. Safety – National Studies Maryland – 8 single-lane rural roundabouts studied Each replaced stop signs or intersection control beacons Source – Maryland State Highway Administration, 2001

21. Safety – National Studies • Insurance Institute for Highway Safety - 2000 • Crash Reductions Following Installation of Roundabouts in the United States • 24 intersections in 8 states converted to roundabouts • 39% Reduction in All Crashes • 76% Reduction in Injury Crashes

22. Safety – National Studies Source – Insurance Institute for Highway Safety and NYSDOT, 2003

23. -60% SIMILAR NCHRP Report 572-Roundabouts in the US (2007)

24. Safety – Increased Ped Safety Source – Roundabouts: An Informational Guide (FHWA)

25. Safety – Increased Ped Safety • Shorter crossing distance • Pedestrian only looks one direction • Drivers at signals watch the light • Drivers at typical intersections tend to look left and turn right • Pedestrian crossing separated from intersection – allows driver to pay more attention to pedestrian

26. Safety –Pedestrian Safety • Disadvantage is that vehicles aren’t necessarily stopping • Reduced speeds help • Possible issues with visually-impaired pedestrians

27. Safety – Pedestrians Literature Review on Vehicle Travel Speeds and Pedestrian Injuries – Final Report DOT HS 809 021, October 1999

28. Safety – Pedestrians United Kingdom Experience Source – TRRL Lab Report 1120, 1984

29. Safety – Pedestrians • Pedestrian Study in Melbourne, Victoria (Australia) • Source: Andrew O’Brien & Associates Pty Limited • Roughly the same size/population as 7 County Twin Cities Metro area • ~4000 roundabouts • 1996-2000 • 57 total pedestrian crashes from 1371 overall crashes • 0 fatalities • 32% required hospitalization

30. Safety – Pedestrians • Victoria, Australia anecdotal experience • Source: Andrew O’Brien & Associates Pty Limited • Black Spot Program – fix intersections with serious crash rates – to be eligible, there must be 3 injury/fatal crashes in a 3 year timeframe • Over 5000 roundabouts in Victoria • Roughly the same size/population as MN • All pedestrian black spot intersections in Victoria are signals

31. Advantages • Reduced environmental impacts • Less fuel consumption • Vehicle emissions reduced • 33% less hydrocarbons • 36% less CO • 21% less nitric oxides • More pleasant to live next to…

32. Case Study – TH 13 and Scott County Rd 2

33. Case Study – TH 13 and Scott County Rd 2 • Rural TWSC Intersection of High-Speed Roads • 2000-2004 (5 year period) • 26 injury, 9 property damage, 2 fatal crashes • 50 injuries and 2 fatalities • Roundabout opened to traffic in Sept 2005 • Sept 2005 - August 2010 • 5 reported crashes • 3 injuries and no fatalities

34. Case Study – Golden, CO • South Golden Road in Golden, Colorado • Before condition • ¾ mile segment of 4-lane expressway with TWLTL • Almost indiscriminate private business driveways • Two signals – Ulysses and Johnson • Proposed additional signal in corridor • Corridor serve several residential neighborhoods, many businesses including fast food restaurants and gas stations, and other retail outlets • High and middle schools located ¼ mile from corridor Source: Alex Ariniello, LSC Transportation Consultants

35. Case Study – Golden, CO South Golden Road before improvements

36. Case Study – Golden, CO 4 roundabouts constructed in 1998 – 99

38. South Golden Road Experience Roundabouts in Series (2004 information) • Travel Time through Corridor Reduced • 78 sec (expected to go to 103 sec) to 68 sec • Intersection Delay Reduced • Access to Businesses Delay Reduced • Before – average 28 seconds, maximum 118 seconds • After – average 13 seconds, maximum 40 seconds • Right turn/U-turn Safer and Quicker than Left Turn In • 85th percentile Speed Reduced from 47 mph to 33 mph

39. South Golden Road Experience Roundabouts in Series Accident Statistics Provided by Public Works Director

40. Good for Businesses • In 2004, sales tax revenues had increased 60% since roundabouts constructed – only portion of city that had seen increase each year, even during an economic slowdown. Plus, over 75,000 sq ft additional retail/office space added.

41. Where are Roundabouts Appropriate? • Entering volumes less than 8,000 vph • Roughly same functional classification • Arterial/arterial, collector/arterial, collector/collector • Entry volumes balanced = higher capacity • The upper capacity limits of a roundabout will be higher with balanced flows. • However, this guideline depends on overall volume. • Heavy mainline travel (ie 90/10) – signal may outperform a roundabout, but needs to be analyzed on a case by case basis. • All levels of pedestrian volumes

42. Locations Not Recommended for a Roundabout • Corridors with a well operating coordinated signal system • Where Satisfactory geometric designs can’t be provided (doesn’t have to be ideal) • Deflection • Inscribed circle diameter • Roadway width • Approach grades

43. Where Roundabouts May “Shine” • Locations with unusual geometry or number of legs • Rural intersections with high crashes or high delay • Intersections with high amounts of left turns on one or more legs • Interchange locations with right of way, bridge width, or bridge crest restrictions • Near schools or playgrounds • Through small towns or commercial corridors (combined with access management)

44. What About Multi-lane Roundabouts? • Concern that MN drivers will find them confusing • Nationwide experience • Similar amount of crashes as signals • Still ~75% reduction in injury crashes • Most typical crashes are caused by not following the signs • Failure to yield to both lanes at entry • Exit conflict • Some education efforts underway • Best advice – follow the signs and pavement markings

45. What About Multilane Roundabouts?

46. What’s Mn/DOT Doing? • Developed Roundabout Chapter in Road Design Manual • Intersection Control Evaluation • Any intersection that requires more than a TWSC will require ICE to choose correct intersection application • All way stop • Signal • Roundabout • Other

47. What’s Mn/DOT Doing? • Roundabout projects will have extra reviews • Same level of reviews as freeways • Roundabout Review Team • Updated State Aid Roundabout Design Checklist • Guidance to cities and counties • Updating Minnesota Manual of Traffic Control Devices • Based on Federal MUTCD (2009) • Many changes for roundabouts

48. What’s Mn/DOT Doing? • Education efforts • Roundabout webpage – googlemndot roundabouts • “Roundabout on a stick” – handed out last year at State Fair • Minnesota State Map • Per project • Washington County Roundabout “U” - google roundabout u

49. Roundabouts in MN • State Highway System (existing) • I-35 and Steele County Road 12 near Medford Outlet Mall (2 at ramp intersections) • TH 13 and Scott County Road 2 near New Prague • Elm Creek Roundabout in Maple Grove (connected to future TH 610) • TH 7 with TH 25 and Carver County Road 10 • TH 61 and Jamaica Avenue in Cottage Grove (2 at ramp intersections) • TH 3 and 190th Street in Farmington/Empire Township

50. Roundabouts in MN • State Highway System (existing) • TH 3 and 80th Street East in Inver Grove Heights • TH 52 and Wentworth Avenue in West St. Paul and South St. Paul (2 at ramp intersections) • TH 284 and 15th Street in Waconia • TH 19 and Chalupsky Ave in New Prague • TH 19 and Alton Ave in New Prague • All roads – State Aid Office List (self-reporting) • 80 constructed and in operation as of Feb 2010 • http://www.dot.state.mn.us/stateaid/ - Roundabout List