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Design Topics

Roundabouts an Informational Guide - Second Edition  TRB’s National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide – Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts.

Access Management and Roundabout Design

Design Checklist

  • Feasibility analysis
  • Preliminary design
  • Final design

Design for Pedestrians and Bicycles

  • Crosswalk location
  • Flashers
  • Marked versus unmarked crosswalks
  • Alternate pavement
  • Pedestrian tunnels--Swedish style
  • Bike Lanes or not in roundabout
  • Pedestrian FAQ :(from Walkinginfo.org)

Minimum Diameter for Trucks

  • AutoTurn
  • Truck aprons
  • Cross slope effects

Capacity Analysis

  • VISSIM:Verkehrs Im Stadt SIM
  • SIDRA SIDRA Intersection Circulation Lane Widths Acceptable Grades Cross Slopes and Drainage

Minimum Slopes

Crowns

Lighting: Good street lighting is a standard safety element of modern roundabout design. Motorists approaching at night must see that the intersection has a central island and that one can no longer drive straight through the intersection. Good street lighting is needed so that cyclists, motorcyclists, and pedestrians can be seen in the roundabout an don the approaches at night. For this reason additional street lights should be installed at roundabouts and on the approaches back a distance of over 150 feet from the yield lines. The lighting design should provide at least 1.9 footcandles of horizontal luminance. Street lights evenly spaced in a ring around the outside of roundabouts and along the approaches to roundabouts works the best.
Uniformity, MUTCD, Europe versus USA:

  • Yield ahead sign
  • YIELD signs
  • Chevron sign
  • ONE-WAY sign
  • Object sign
  • Crosswalk Warning sign
  • Circular Roundabout Warning sign
  • Speed Advisory sign
  • Street sign
  • Directional or route sign

Landscaping: The central islands of roundabouts allow for attractive landscaping. To provide adequate stopping sight distance for circulating traffic, the outer margins of the central islands must have low ground covers. The central portions of these islands will be available for objects of any height, including trees, walls, and public art. The Colorado towns of Vail and Avon, and the cities of Addison Park, Texas and Las Vegas, Nevada offer good examples of beautiful community entry statements created by roundabouts. Signing and Striping

Center Island Design

  • Art and fountains - Thousands of Example photos inside the center islands France Examples  (by MarcLescuyer). Hit "LES PHOTOS" button, then "ENVOYER" button to the right of "Liste alphabétique".

Design Elements

  • Truck aprons
  • Curb types
  • Landscaping
  • Lighting design

Cost Estimates

  • Right of way
  • Pavement
  • Landscaping
  • Lighting
  • Grading and drainage

Definitions

  • Inscribed circle diameter (ICD)
  • Entry flare
  • Deflection

Roundabouts USA is © Copyright Bill Baranowski

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