Progress withroundabouts

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Progress withroundabouts

  1. 1. Ourston Roundabout Engineering Progress with Roundabouts to Date Mark Lenters, President, Ourston Roundabout Engineering Inc. mlenters@ourston.com www.ourston.com 1 Progress by State Ourston Roundabout Engineering www.ourston.com 2 1
  2. 2. 1990: The First U.S. Modern Roundabouts Town Center Drive, Summerlin, Nevada Ourston Roundabout Engineering www.ourston.com 3 U.S. Since 1990 • 1990: Modern roundabouts built in Las Vegas. • 1995: UK style roundabouts replace signals & create “Roundabout Valley” in Avon/Vail, CO. • 1997: HCM adds roundabouts • 2000 and 2010: FHWA Roundabouts: An Informational Guide • 2010 HCM soon to be released • US Currently building ~ 350 per year, and rising. Ourston Roundabout Engineering www.ourston.com 4 2
  3. 3. National Collision Statistics • Original 24 roundabouts before and after (c. (c 2000) • Reduction in injuries = 76% • Combined reduction of all crashes = 40% • Follow-up study combining results of 55 sites 1998 - 2003: • 70% reduction in injuries • 35% reduction in all collisions combined • Similar to international statistics Ourston Roundabout Engineering www.ourston.com 5 National collision statistics for multi-lane roundabouts Reduction in All Types Intersection Type Before of Collisions with Roundabouts Traffic Signals 67% All-Way Stop Control 12% Two-Way Stop Control 19% Suburban Two-Way Stop Control 18% Urban Note: Results based on a study of 26 multi-lane intersections converted to multi-lane roundabouts with 3 years of before and after data (source: NCHRP Report 572, 2006) Ourston Roundabout Engineering www.ourston.com 6 3
  4. 4. Roundabout collisions = low severity (incorrect lane choice) Ourston Roundabout Engineering www.ourston.com 7 Roundabout collisions = low severity (failure to yield) Ourston Roundabout Engineering www.ourston.com 8 4
  5. 5. Teaching drivers ..at the at roundabout entry during opening Ourston Roundabout Engineering www.ourston.com 9 Ourston Roundabout Engineering Roundabout Site Selection Mark Lenters, President, Ourston Roundabout Engineering Inc. mlenters@ourston.com www.ourston.com 10 5
  6. 6. Identifying Candidate Intersections Local and State Initiatives: • Safet Improvements Safety Impro ements • Congestion relief • Development permit The Key mindset: - Be sure to solve a problem if a roundabout is to be used! Ourston Roundabout Engineering www.ourston.com 11 Selection process includes: 1. Initial planning level assessment performed as pa o a s udy to e a ua e the o e a part of study o evaluate e overall appropriateness of a roundabout; 2. Roundabout study considers site-specific conditions: • A safety assessment • Operational performance • Cost comparison 3. Requirements for drainage, lighting and public outreach. Ourston Roundabout Engineering www.ourston.com 12 6
  7. 7. Locations where roundabouts are suitable: 1. Safety – Intersections with historically high crash rates. – Roads with a historical problem of excessive speeds speeds. – Intersections with more than four legs or with difficult skew angles 2. Operations – A high % of turning movements and intersections that must accommodate U-turns. – High traffic volumes at peak hours – Intersections where widening one or more approach may be difficult or cost-prohibitive. – Ramp terminal intersections Ourston Roundabout Engineering www.ourston.com 13 Locations where roundabouts are suitable: Cont’d… • Intersections with high traffic growth (A single-lane roundabout staged f expansion t two lanes) d b t t d for i to t l ) • Transitions between rural and urban - gateways 3. Traffic Control • Existing two-way stop-controlled intersections that do not meet signal warrants. • Intersections or corridors where traffic calming is a desired outcome of the project. 4. Aesthetics • Focal point for a community, gateway or themed development Ourston Roundabout Engineering www.ourston.com 14 7
  8. 8. Initial Screening ADT Thresholds Ourston Roundabout Engineering www.ourston.com 15 Typical Roundabout Capacity Ranges Typical Daily Service Typical Inscribed Circle Roundabout Type Volume2 (vpd) Diameter1. 4-leg roundabouts Mini-Roundabout 45-80 ft (14-28 m) Less than 30,000 Urban Single-Lane 100 -150 ft (30 – 50 m) less than 25,000 Urban Multilane 160 - 215 ft (50 – 65 m) 25,000 to 55,000 (2-lane entry) Urban Multilane (3 or 4-lane 215 - 275 ft (65 – 85 m) 55,000 to 80,000 entry) Rural Single-Lane 130 -150 ft (35 – 55 m) less than 25,000 Rural M ltil R l Multilane 165 - 215 ft (50 – 65 m) 25,000 to 55,000 (2-lane entry) Rural Multilane 215 – 300 ft (65 – 85 m) 55,000 to 70,000 (3-lane entry) 1 Diameters are for general guidance. 2Capacities vary depending on entering volume and turning / circulating flow. Ourston Roundabout Engineering www.ourston.com 16 8
  9. 9. Conditions that may eliminate roundabout: 1. Coordinated signal system (platooned traffic) 2. R/W impacts 3. Inadequate SSD 4. Steep grades 5. Minor improvement is that are more cost- e ect e effective: • No R/W required • Extend left turn bay • Add turn bay in existing median Ourston Roundabout Engineering www.ourston.com 17 Conditions that may eliminate roundabout: 6. Intersections in close proximity to a signalized intersection (e.g., coordinated arterial signal systems) 7. Locations with steep grades and unfavorable topography that may limit visibility or an acceptable layout for a roundabout. 8. Intersections in close proximity to an at-grade railroad crossing. 9. Intersections where an unacceptable delay to the major p y j road could be created (90% main street traffic). 10. Heavy pedestrian or bicycle movements that may require signals. Ourston Roundabout Engineering www.ourston.com 18 9
  10. 10. Intersection Control Study 1. Project Background: describe site conditions 2. Safety Assessment (historical crash data) y ( ) 3. Alternate Sketches – lane configuration, rough alignment 4. Operational Analyses – Arcady, HCM 5. Cost Comparison – Construction, crash savings, life- cycle 6. Alternative Selection – screening criteria (capacity, safety, safety cost) 7. Conceptual Roundabout Design – nearly a 30% design 8. Conclusions and Recommendations Ourston Roundabout Engineering www.ourston.com 19 Ourston Roundabout Engineering Challenging but successful examples: - Railways - Corridors - Schools - Interchanges - Unusual geometry - Pedestrians - Closely space intersections - Rural intersections - Access management www.ourston.com 20 10
  11. 11. Daingerfield, TX Ourston Roundabout Engineering www.ourston.com 21 Daingerfield, TX Ourston Roundabout Engineering www.ourston.com 22 11
  12. 12. Corridor – Golden, CO • 4 Signals changed to RBTS • 60% ddrop i C h R t in Crash Rate • 94% drop in injuries – From 31 in 3 yrs to only one: a median opening left turn crash • No Pedestrian crashes • Single lane RBT has fewest 23 Space and cost savings in a corridor... Avon Colorado - Arterial Corridor, 1997 Ourston Roundabout Engineering www.ourston.com 24 12
  13. 13. Replaced traffic signals at main intersection Ourston Roundabout Engineering www.ourston.com 25 Two decades of planned expansion Second interchange for Wal-Mart in 2003 Ourston Roundabout Engineering www.ourston.com 26 13
  14. 14. Two interchanges in Vail, 1995 Interchange intersections previously controlled by police. Ourston Roundabout Engineering www.ourston.com 27 Unusual Geometry Avoided impacts to buildings & parking lots Ourston Roundabout Engineering www.ourston.com 28 14
  15. 15. Pedestrian Signals At Roundabouts Ourston Roundabout Engineering 29 www.ourston.com www.ourston.co Closely Spaced Intersections Lee Rd @ Whitmore Lake Rd and US-23, Metro Detroit Ourston Roundabout Engineering www.ourston.com 30 15
  16. 16. Rural High Speed Hwy. 85/Hwy. 17, 2006 Ourston Roundabout Engineering www.ourston.com 31 Access Management Loveland, CO Narrow Median possible because roundabouts b d b t allow U-turns Ourston Roundabout Engineering www.ourston.com 32 16
  17. 17. Rocky Mountain Avenue - 2008 Business is still thriving Ourston Roundabout Engineering www.ourston.com 33 Closely Spaced Intersections Lee Rd @ Whitmore Lake Rd and US-23, Metro Detroit Ourston Roundabout Engineering www.ourston.com 34 17
  18. 18. Contiguous Roundabouts Ourston Roundabout Engineering www.ourston.com 35 Access Management • Minor driveways can be designated as in intersection leg for access near entries or exits Ourston Roundabout Engineering www.ourston.com 36 18
  19. 19. Transition Between Urban Forms (Clearwater Beach, FL) Commercial with angle parking Photo: City of Clearwater FL r, Residential Ourston Roundabout Engineering www.ourston.com 37 J.F.K. Middle School, Clearwater, FL (>50 others like it in the U.S. being tracked) Ourston Roundabout Engineering www.ourston.com 38 19
  20. 20. Non-Conforming Circle Becomes a Roundabout (Long Beach, CA, 1992) Ourston Roundabout Engineering www.ourston.com 39 Ourston Roundabout Engineering Achieving Success Using Roundabouts Mark Lenters, President, Ourston Roundabout Engineering Inc. mlenters@ourston.com www.ourston.com 40 20
  21. 21. The Recipe for Successful Use of Roundabouts • Lead with an Area-Wide Policy: – Roundabouts shall be considered when… – Conduct Alternatives Analyses (life cycle) – Top-down consensus building – Only use roundabouts to solve a problem 1.Assemble general policy tools 2.Develop project specific tools Ourston Roundabout Engineering www.ourston.com 41 General and Specific Outreach Tools General Tools Project Specific Tools • Case studies • Scale model • Testimonials • Animation/simulation • National statistics • Renderings • How-to videos • Project web page • Web-cam • Project brochure • Driver training • Website • Brochures Ourston Roundabout Engineering www.ourston.com 42 21
  22. 22. Scale Model (1:87 = ‘HO’ scale) Ourston Roundabout Engineering www.ourston.com 43 Coordination of Geometry and Lane Designation 44 22
  23. 23. SB Pioneer Road Movement Ourston Roundabout Engineering 45 www.ourston.com NB Belt Line Road Movement Ourston Roundabout Engineering 46 www.ourston.com 23
  24. 24. Area-wide Education Campaigns • Making Pedestrians more active… Ourston Roundabout Engineering www.ourston.com 47 24

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