KAI - Modern Urban Roundabouts

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The following presentation created by Kittelson & Associates, Inc. (KAI), provides an overview Modern Urban Roundabouts.

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  • x New Guidance on Roundabouts October 2, 2009 Kittelson & Associates, Inc.
  • KAI - Modern Urban Roundabouts

    1. 1. Modern Urban Roundabouts December 15, 2009
    2. 2. Roundabouts are a subset of circular intersections… Roundabouts Rotaries Neighborhood traffic circles All circular intersections Others
    3. 3. Rotary: US 377/TX 183/Camp Bowie Pkwy, Fort Worth, TX Photo: City of Fort Worth, TX
    4. 4. Conversion of Rotary to Roundabout: Kingston, NY Photo: New York State DOT
    5. 5. Roundabouts versus Other Circular Intersections <ul><li>Key elements distinguish roundabouts: </li></ul><ul><ul><li>YIELD control on entry </li></ul></ul><ul><ul><li>Priority to circulating vehicles </li></ul></ul><ul><ul><li>Slow, consistent speeds </li></ul></ul><ul><ul><li>Pedestrian access & crossing </li></ul></ul><ul><ul><li>Parking </li></ul></ul><ul><ul><li>Direction of circulation </li></ul></ul>
    6. 6. Yield on entry Photos: Lee Rodegerdts Roundabout Traffic Circle <ul><li>Higher capacity </li></ul><ul><li>Lower delay </li></ul>
    7. 7. Priority to Circulating Vehicles Photos: Lee Rodegerdts Roundabout Traffic Circle <ul><li>Prevents gridlock </li></ul>
    8. 8. Pedestrian Access Photo: Oregon DOT Photos: Lee Rodegerdts Roundabout Traffic Circle
    9. 9. No Parking within Roundabout Photos: Lee Rodegerdts <ul><li>Parking within roundabout: </li></ul><ul><ul><li>Increases conflicts </li></ul></ul><ul><ul><li>Reduces circulating capacity </li></ul></ul>Roundabout Traffic Circle
    10. 10. Direction of Circulation Photo: Ken Courage Photo: Lee Rodegerdts Roundabout Traffic Circle
    11. 11. Key Roundabout Features Exhibit 1-1, p. 6
    12. 12. Our recent history has been active… 1990 1995 2000 1905: Columbus Circle (NYC) 1990: First modern use in U.S. 1920s-1950s: Rotary era 2009-2010: Updated FHWA Rbt Guide, MUTCD, HCM 2005 2010 1990s: MD, FL, O&D Guides 2001-2007: Explosion of state guides and manuals 2000: FHWA Rbt Guide 2007: NCHRP Report 572
    13. 13. Number built each year is going up exponentially
    14. 14. U.S. sites by state through 1992
    15. 15. U.S. sites by state through 1997
    16. 16. U.S. sites by state through 2002
    17. 17. U.S. sites by state through 2007
    18. 18. NCHRP Report 572 <ul><li>“Roundabouts in the United States” </li></ul><ul><li>Most comprehensive study of U.S. roundabout performance to date </li></ul><ul><li>Scope (NCHRP Project 3-65): </li></ul><ul><ul><li>Safety and operational models based on U.S. field data </li></ul></ul><ul><ul><li>Updated design guidance based on model findings and current state-of-the-art practice and thinking </li></ul></ul><ul><li>Completed May 2006 </li></ul>
    19. 19. NCHRP 3-65A: Update of Roundabout Guide <ul><li>FHWA Roundabout Guide has become a popular and standard reference </li></ul><ul><li>Guide has become out of date with rapid increase in U.S.-based experience and research </li></ul><ul><li>Update in 2010 </li></ul>
    20. 20. Categories of Roundabouts
    21. 21. Mini-Roundabout
    22. 22. Mini-Roundabout Examples – U.S. Dimondale, MI Photo: Lee Rodegerdts Lutherville, MD Photo: Maryland SHA
    23. 23. Mini-Roundabout Examples - Europe Photo: Lee Rodegerdts Germany United Kingdom Photo: Werner Brilon
    24. 24. Urban Compact Roundabouts
    25. 25. Urban Compact Roundabout Examples West Boca Raton, FL Germany Photo: Lee Rodegerdts Photo: Werner Brilon
    26. 26. Urban Single-Lane Roundabouts
    27. 27. Urban Single-Lane Roundabout Examples Santa Barbara, CA Bend, OR Photo: Lee Rodegerdts Photo: Oregon DOT
    28. 28. Urban Double-Lane Roundabouts
    29. 29. Urban Double- and Multi-Lane Roundabout Examples Towson, MD Avon, CO
    30. 30. Rationale for Considering a Roundabout <ul><li>Safety </li></ul><ul><li>Operations </li></ul><ul><li>Land Use </li></ul><ul><li>Geometry </li></ul>
    31. 31. Rationale: Safety <ul><li>Roundabouts have a proven safety record for reducing motor vehicle crashes, particularly injury crashes </li></ul><ul><li>Experience is due to basic contributing factors: </li></ul><ul><ul><li>Reduced vehicle speeds </li></ul></ul><ul><ul><li>Reduced driver decisions </li></ul></ul><ul><ul><li>Reduced conflict points </li></ul></ul><ul><ul><li>Reduced conflict severity </li></ul></ul>
    32. 32. U.S. Experience NCHRP Report 572 Results (May 2006) 82 44 Two-way stop (36) No significant change No significant change All-way stop (10) 78 48 Signalized (9) 76 35 All sites (55) % Reduction in Injury Crashes % Reduction in All Crashes Group Characteristic before Conversion (sample size)
    33. 33. Maryland’s Roundabout Accident Experience (March 2007 Study) Accident data at 15 state highway intersections converted to single-lane roundabouts between April 1993 and December 2003 86% reduction 0.16 1.13 Mean injury accident rate (acc./MEV) 68% reduction 0.61 1.91 Mean total accident rate (acc./MEV) 83% reduction 7.3 43.5 Total annual injury accidents 65% reduction 24.8 71.7 Total annual accidents % Change After Before
    34. 34. Maryland’s Roundabout Accident Experience (cont.) <ul><li>Overall Crash Reductions: </li></ul><ul><ul><li>100% reduction in fatal accident rate </li></ul></ul><ul><ul><li>86% reduction in injury accident rate </li></ul></ul><ul><ul><li>40% reduction in property damage only accidents </li></ul></ul><ul><li>Benefit/cost analysis indicated return of $13 for every dollar spent. </li></ul>
    35. 35. Lower speed is safer for pedestrians Chance of pedestrian death increases with vehicle speed Source: United Kingdom
    36. 36. Number of driver decisions: REDUCED <ul><li>Entry into only one conflicting traffic stream </li></ul><ul><li>Conflicting speeds fairly uniform </li></ul><ul><li>Conflicts with pedestrians physically separated from conflicts with other vehicles </li></ul>
    37. 37. Vehicle Conflict Points: REDUCED Crossing conflicts eliminated at roundabout Merging Diverging Crossing
    38. 38. Severity of Vehicular Conflicts: REDUCED <ul><li>Severity related to relative velocities of conflicting streams </li></ul>Rear-end Sideswipe Angle Angle Head-on Least severe Most severe
    39. 39. Rationale: Operations <ul><li>May solve an existing or projected operational problem </li></ul><ul><li>Possible candidates </li></ul><ul><ul><li>Heavy delay on minor road </li></ul></ul><ul><ul><li>Large traffic signal delays </li></ul></ul><ul><ul><li>Heavy left turning traffic </li></ul></ul><ul><ul><li>Traffic patterns uncertain or changeable (no signal timing plans to keep updated) </li></ul></ul>
    40. 40. Roundabouts versus Signals: MUTCD Signal Warrant Threshold 0 2 4 6 8 10 12 14 16 18 20 600 700 800 900 1000 1100 1200 1300 1400 1500 Total Major Street Volume (veh/h) Average Delay (s/veh) Signal (10% left turns) Signal (50% left turns) Roundabout (10% left turns) Roundabout (50% left turns) Exhibit 3-7, p. 63 Based on MUTCD Warrant 3 (2000 ed.)/Warrant 11 (1988 ed.)
    41. 41. Rationale: Land Use <ul><li>Reasons other than safety or operations </li></ul><ul><li>Possible candidates </li></ul><ul><ul><li>Community enhancement </li></ul></ul><ul><ul><li>Gateway treatment </li></ul></ul><ul><ul><li>Break between conflicting land uses </li></ul></ul><ul><ul><ul><li>Urban vs. rural </li></ul></ul></ul><ul><ul><ul><li>Commercial vs. residential </li></ul></ul></ul>
    42. 42. Example of Land Use: Clearwater, FL Photo: City of Clearwater, FL Commercial w/ angle parking Residential
    43. 43. Rationale: Geometry <ul><li>Unusual geometric configurations may lend themselves to a roundabout </li></ul><ul><li>Possible candidates </li></ul><ul><ul><li>More than four legs </li></ul></ul><ul><ul><li>“Y” configuration with high-speed movements </li></ul></ul><ul><ul><li>Need for U-turns </li></ul></ul><ul><ul><li>Freeway interchange ramps </li></ul></ul>
    44. 44. Consideration of Users <ul><li>Design Vehicle </li></ul><ul><li>Pedestrians </li></ul><ul><li>Bicycles </li></ul><ul><li>Emergency Vehicles </li></ul>
    45. 45. Design vehicle Photos: Lee Rodegerdts Truckee, California Portland, Oregon
    46. 46. Design for Appropriate Design Vehicle: Critical at Planning Stage Photos: Lee Rodegerdts <ul><li>May require use of truck apron </li></ul><ul><li>Affects diameter and right-of-way requirements </li></ul>Good design Poor design
    47. 47. Accommodating Pedestrians <ul><li>Influence good driver behavior </li></ul><ul><li>Influence good pedestrian behavior </li></ul>Photos: Lee Rodegerdts
    48. 48. Pedestrian Design Guidance <ul><li>Well defined walkway edges </li></ul><ul><li>Separated walkways </li></ul><ul><li>Detectable warnings </li></ul><ul><li>Perpendicular crossings </li></ul><ul><li>Contrasting crosswalk markings </li></ul>3 2 1 4 5
    49. 49. Discourage travel to central island <ul><li>Use care in selecting central island treatments </li></ul><ul><li>Consider different pavement texture for truck apron </li></ul>Photo: Scott Beaird Photo: Erin Ferguson
    50. 50. Improving Accessibility for All Pedestrians <ul><li>Key issues </li></ul><ul><ul><li>Guiding pedestrian navigation (wayfinding) </li></ul></ul><ul><ul><li>Promoting vehicular yielding </li></ul></ul><ul><ul><li>Providing indications that vehicle has yielded </li></ul></ul><ul><ul><li>Providing equal access to public facilities </li></ul></ul>Photo: Lee Rodegerdts
    51. 51. Accessibility for Visually Impaired <ul><li>Access Board proposing requiring some kind of signals for multilane entries and exits </li></ul><ul><li>Michigan case settlement  hybrid pedestrian signals (HAWK signals) being installed </li></ul><ul><li>Practice will continue to evolve </li></ul>
    52. 52. Pedestrian hybrid signal: Golden, CO Photo: Lee Rodegerdts
    53. 53. Bicycles <ul><li>Roundabouts slow vehicles to speeds compatible with bicycles </li></ul><ul><li>Bicycle speeds: 10-15 mph </li></ul><ul><li>Bicyclists have wide range of skills and comfort levels in mixed traffic </li></ul><ul><ul><li>Experienced cyclists (e.g., commuter or utility cyclists) </li></ul></ul><ul><ul><li>Inexperienced cyclists (e.g., children or occasional recreation cyclists) </li></ul></ul><ul><li>Give bicyclists option of either being vehicle or pedestrian </li></ul>
    54. 54. Example Bicycle Treatments
    55. 55. Bicycle Treatments: Grand Junction, CO Source: City of Grand Junction, CO
    56. 56. Public Involvement: Overall Experience <ul><li>Typical experience (but not always): negative reaction before construction, positive reaction after construction </li></ul><ul><li>Common misconception based on rotaries or neighborhood traffic circles </li></ul>
    57. 57. NCHRP Synthesis 264 (Jacquemart) Before Construction After Construction
    58. 58. Project Techniques: Public meeting displays Model created by Missouri D.O.T. Photo: Missouri DOT
    59. 59. Project Techniques: Educating School Age Children (Overland Park, KS) Photo: Erin Ferguson
    60. 60. Project Techniques: Brochures (Vail, CO) Exhibit 2-6(a), p. 42
    61. 61. Project Techniques: Videos <ul><li>General information </li></ul><ul><ul><li>“ Modern Roundabouts” (Maryland SHA) </li></ul></ul><ul><ul><li>“ A User’s Guide to Roundabouts” (Oregon DOT, 1999) </li></ul></ul><ul><ul><li>“ Driving Modern Roundabouts” (Washington State DOT/City of Lacey/City of Olympia) </li></ul></ul><ul><li>Project-specific information </li></ul><ul><ul><li>“ The East Topeka Roundabouts” (Kansas DOT, 2000) </li></ul></ul><ul><ul><li>“ I-70/Vail Road” (Ourston & Doctors) </li></ul></ul><ul><ul><li>“ Nonconforming Traffic Circle Becomes Modern Roundabout” (Ourston & Doctors) </li></ul></ul><ul><li>Specialty information </li></ul><ul><ul><li>“ Snow at Roundabouts” (Ourston & Doctors) </li></ul></ul>
    62. 62. Sample State Web Site: Maryland State Highway Administration
    63. 63. La Jolla Boulevard – Bird Rock Roundabouts
    64. 64. Case Study – Campus Drive/Daggett Avenue <ul><li>Year 2006 Conditions </li></ul><ul><ul><li>v/c ratio = 0.77 </li></ul></ul><ul><ul><li>LOS = F </li></ul></ul><ul><ul><li>5 years of safety data </li></ul></ul><ul><ul><ul><li>13 crashes </li></ul></ul></ul><ul><ul><ul><li>mostly angle crashes </li></ul></ul></ul><ul><li>Year 2013 Conditions </li></ul><ul><ul><li>Includes OIT Expansion </li></ul></ul><ul><ul><li>v/c ratio > 1.0 (peak 15 mins) </li></ul></ul><ul><ul><li>LOS = F </li></ul></ul><ul><ul><li>Does not meet signal warrants </li></ul></ul><ul><li>Year 2013 Mitigated Conditions </li></ul><ul><ul><li>Single-lane roundabout </li></ul></ul>A A A A LOS 0.08 0.23 0.49 0.47 v/c W E S N
    65. 65. Case Study – Campus Drive/Daggett Avenue N Opportunities to improve ped/bike facilities Minimal ROW needs Reduction to one travel lane Roundabout? Example ped/bike improvements
    66. 66. Key Issues for Now and Future <ul><li>Continued education of public </li></ul><ul><ul><li>Roundabout is just another type of intersection </li></ul></ul><ul><li>Continued education of professionals </li></ul><ul><ul><li>Roundabouts should always be considered as a potential solution </li></ul></ul><ul><li>Continued involvement in standards/policy/guidance development </li></ul><ul><ul><li>Our profession and our communities benefit from us coming together and collectively improving our practice </li></ul></ul>
    67. 67. Thank You! Photo courtesy of Harper Houf Peterson Righellis, Inc.

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