What s New in Roundabout Design?

Transcription

1 Roundabouts: An Informational Guide, 2 nd ed. What s New in Roundabout Design? National and State Perspective Brian Walsh, WSDOT Lee Rodegerdts, Kittelson & Associates, Inc. Overview & Philosophy Chapter-by-Chapter Discussion Example Applications ITE Quad Conference Lynnwood, WA April 19, 2011 Overview Overview (cont.) Work conducted under NCHRP Project 3-65A Work published as NCHRP Report 672 Co-branded by FHWA Builds extensively on the first edition (2000) Based on established and emerging U.S. practices and recent research Less exclusive reliance on international practice More US empirical experience and examples Alignment with other documents Highway Capacity Manual 2010 Highway Safety Manual, 1 st Edition 2009 Manual on Uniform Traffic Control Devices IESNA Roundabout Lighting Design Guide Philosophy Outline Principle-based approach Recognizes roundabouts, as with any intersection treatment, requires the balancing of competing objectives Flexibility is provided to encourage independent designs and techniques Tailored to particular situations Emphasizes performance-based evaluation of designs Allows development of new techniques More than one way to achieve an acceptable design Front Material 1. Introduction 2. Roundabout Considerations 3. Planning 4. Operations 5. Safety 6. Geometric Design 7. Application of Traffic Control Devices 8. Illumination 9. Landscaping 10. Construction and Maintenance Appendices Note: Old Chapter 8 (System Considerations) material now put into other chapters. Kittelson & Associates, Inc. 1

2 Roundabouts: An Informational Guide, 2 nd ed. Chapter 1: Introduction Overview & Philosophy Chapter-by-Chapter Discussion Example Applications What is a roundabout? How are they different from other circular intersections? Scope and purpose of the guide Ch 1 (cont.): Categories Reduced from Six to Three Chapter 2: Roundabout Considerations Mini-roundabout Single-lane Multilane Mini-Roundabout Dimondale, Michigan Single-lane Roundabout Skagit County, Washington Multilane Roundabout Carmel, Indiana General characteristics Advantages and disadvantages Safety User decisions Operations Spatial considerations Access management Environmental factors Operations and maintenance costs Traffic calming Aesthetics User considerations Policy and legal issues Chapter 3: Planning Chapter 3 (cont.): Updated planning-level capacity figure New information on range of potential applications Intended to demonstrate breadth of feasibility Discussion of considerations for each typical application Updated user education materials Examples of applications 50,000 45,000 40,000 35,000 30,000 Double-lane roundabout may be sufficient (additional analysis needed) Near Schools - Clearwater, Florida High-Speed Roadways - Paola, Kansas Photos: Lee Rodegerdts AA ADT 25,000 Single-lane roundabout may be 20,000 sufficient (additional analysis needed) 15,000 Single-lane roundabout Double-lane roundabout 10,000 likely to operate acceptably likely to operate acceptably 5, % 10% 20% 30% 40% Left-Turn Percentage Photos: Lee Rodegerdts Kittelson & Associates, Inc. 2

3 Chapter 4: Operations Capacity Models in HCM 2010 Based on 2010 edition of the Highway Capacity Manual 1,400 1,200 Chapter presents subset of HCM procedure (incomplete without t HCM 2010) Capacity (pc/h) 1, Capacity of one-lane entry or right lane of two-lane entry against two conflicting lanes Capacity of left lane of two-lane entry against two conflicting lanes Explicit recognition of use of calibrated alternative tools to analyze situations not covered by HCM models 400 Capacity of one-lane or either lane of twolane entry against one conflicting lane 200 Dashed regression extrapolated beyond the data ,000 1,200 1,400 1,600 1,800 2,000 Conflicting Flow Rate (pc/h) Chapter 5: Safety Chapter 6: Geometric Design Principles Observed safety performance Crash prediction methodologies Intersection level Approach level Builds on NCHRP Report 572 research incorporated into the Highway Safety Manual Initial Operational Analysis Identify Initial Design Elements Single-Lane Multilane Mini- Roundabouts Roundabouts Rbts Check Performance Other Input (env., PI) Iterate Design Details and Applications Chapter 6 (cont.): Principles Ch 6 (cont.): Alignment Fastest path Path alignment Design vehicle Non-motorized design users Sight distance and visibility Visibility/view angles Offset left, radial, and offset right each have their place Each circumstance requires its own solution, with principles determining tradeoffs Words preferred, acceptable, and avoid have been removed Kittelson & Associates, Inc. 3

4 Chapter 6 (cont.): Multilane Roundabouts Chapter 6 (cont.): Pedestrian and Bicycle Treatments Same challenges as single-lane roundabouts, plus: Lane use and assignment Path alignment Management of conflict areas Updated to reflect latest research, practices, and policies Chapter 7: Application of Traffic Control Devices Chapter 7 (cont.): Circulatory Roadway Marking Options Complements 2009 MUTCD Discusses applications of signs, markings, and signals/beacons Discussion of variations that used by some agencies Chapter 8: Illumination Chapter 9: Landscaping Provides several useful resources for roundabout lighting Discuss principles Visibility from a distance Visibility of key conflict areas Lighting levels Equipment type/location Pole location Example illumination layouts Photo: Lee Rodegerdts Emphasis on visibility and focus of driver attention Expanded discussion of landscaping context Lower speed urban environments typically provide more flexibility than higher speed suburban or rural environments Discussion of tradeoffs with art and other features Photo: Brian Walsh Coralville, Iowa Federal Way, Washington Kittelson & Associates, Inc. 4

5 Chapter 10: Construction & Maintenance Conclusion Construction staging scenarios Public information techniques Maintenance considerations The 2 nd Edition presents a significant update and expansion over the 1 st edition It incorporates US-based research and experience and many more US-based examples and photographs Reorganization of key sections is intended to clarify the emphasis on principles and balancing trade-offs Washington State Department of Transportation Distribution of Roundabouts by Jurisdictional Type in Washington State Washington State Roundabout Distribution State DOT s developing their own specific design guidance or policy to bring some clarity to all the different options for designing roundabouts WSDOT produced this 30 page document in 1999 (original called Chapter 915). It is now on its 3 rd major rewrite. 1 st Federal Highway Administration Guide released in 2000 The Roundabout Chapter is now called 1320 within the WSDOT Design Manual. WSDOT Kittelson & Associates, Inc. 5

6 Chapter 2 Roundabout Considerations Design for Trucks Kittelson & Associates, Inc. 6

7 Planning Chapter 3 Kittelson & Associates, Inc. 7

8 Chapter 6 Geometric Design Kittelson & Associates, Inc. 8

9 Central Island possibilities WSDOT specific Roundabout Curb Detail Chapter 7 Application of Traffic Control Devices Kittelson & Associates, Inc. 9

10 Design Visualization near Walla Walla, WA Existing Proposed Cle Elum, WA portion of Roundabout Braintrust Kittelson & Associates, Inc. 10

11 Roundabout Coordination Group Thank you! Brian Walsh, P.E. Washington State DOT Olympia, Washington (360) Lee A. Rodegerdts, P.E. Kittelson & Associates, Inc. Portland, Oregon (503) Kittelson & Associates, Inc. 11