Guidelines cover policy/guidelines about roundabouts

View DPM Chapter 8

Roundabouts should be designed practically to mitigate costs and construction duration. Practical design does not compromise safety nor eliminate standards and good practice. It does focus on context, need and purpose, and emphasizes engineering judgment. An approach alignment offset left of the circle center is most beneficial to promote gradual speed reduction and yield at entry. Some examples of practical design include:

• Making the most use of existing pavements and profiles
• Mitigate intersection skew angle with ellipse
• Staging an expandable design (size for current traffic demand)
• Blending the new design with the current profile and existing landscape
  

Practical Design Guide

GDOT considers roundabouts as part of the Intersection Control Evaluation (ICE). Each alternative intersection control is evaluated to compare which will operate best as the intersection control.

Roundabouts are considered and weighed based on their operational and safety benefits against other alternative intersection controls.

View ICE Policy

The intersection control evaluation tool evaluates several alternatives. The ICE tool offers single lane and multilane roundabout alternatives as configurations to be considered when evaluating an intersection, along with several other intersection alternatives.

View ICE Tool

SIDRA is most useful when determining the feasibility of a roundabout at an intersection and should accompany any preliminary study. In addition to this tool, there are many software packages available for use, namely RODEL and ARCADY.

GDOT also has a free roundabout analysis tool that is available for engineers that don’t have access to other paid analysis software. The GDOT Roundabout Analysis Tool can be used for preliminary design and planning purposes. As an analysis tool, it provides useful measures such as capacity, queue, and delay by which its operational ability can be assessed. It also allows the designer to quickly determine number of lanes, etc. (single lane, multilane, bypass lanes, etc.).

Download Analysis Tool

Several training classes are available to engineers who work with GDOT.

Classes

Introduction to Roundabouts: Roundabout Planning, Design and Operational Analysis

Course Description

In this course, you will review the planning phase of a roundabout, the operational analysis steps, and detailed design guidelines for roundabouts. The planning phase focuses on where roundabouts should be considered and issues inherent in the design and operation. The operational analysis covers the detailed performance of a roundabout and typical measures of effectiveness, such as capacity, delay, and queues. The design phase includes issues related to size, horizontal and vertical alignment, transit, pedestrians, bicyclists, signing, and striping. In addition, you will perform exercises individually and in team settings and apply and discuss the various elements, standards, and features relevant to the development and design of modern roundabouts.

The basis for the course is the FHWA document, Roundabouts: An Informational Guide, supplements to the FHWA guide, and ongoing instructor involvement in NCHRP research and TRB, ITE, NCUTCD, and IESNA Committees.

Course Topics

• Characteristics of early circular intersections and present-day roundabouts
• Roundabout site selection and planning
• Effectiveness measures for roundabouts
• Roundabout design

If you're interested in attending this course please submit an email with your name and contact information (email and phone)

Email

Introduction to ICE

Course Description

In this course, you will review how to fill in the Intersection Control Evaluation Tool.

Course Topics

• Introduction
• Stage 1
• Stage 2
• Waivers

Roundabout Design Guide Video Training Assistance

Course Description

A package of demonstration videos has been prepared to supplement the published roundabout design guidance. In a series of videos, designers can see demonstrations of how to develop design elements and perform design checks on roundabouts. The videos demonstrate the fundamentals of roundabout design that are explained in the Roundabout Design Guide.

Video Module Topics

• Fastest Path Demonstration
• Design Vehicle Check Demonstration
• Sight Distance Check Demonstration
• How-To: Roundabout Placement
• How-To: Add Right Turn Bypass
• How to: Add Splitter Islands and Pedestrian Accommodations