Roundabouts: An Informational Guide – Second Edition (2010) / Chapter Skim
Currently Skimming:
Pages 1-19
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 1... ...
Chapter 1/Introduction Page 1-1 Roundabouts: An Informational Guide CHAPTER 1 INTRODUCTION CONTENTS 1.1 INTRODUCTION .
|
From page 2... ...
Roundabouts: An Informational Guide Page 1-2 Chapter 1/Introduction LIST OF EXHIBITS Exhibit 1-1 Key Roundabout Characteristics .
|
From page 3... ...
Chapter 1/Introduction Page 1-3 Roundabouts: An Informational Guide 1.1 INTRODUCTION A roundabout is a form of circular intersection in which traffic travels counterclockwise (in the United States and other right-hand traffic countries) around a central island and in which entering traffic must yield to circulating traffic.
|
From page 4... ...
Roundabouts: An Informational Guide Page 1-4 Chapter 1/Introduction way, or yield, to circulating traffic. This rule prevented circular intersections from locking up by not allowing vehicles to enter the intersection until there were sufficient gaps in circulating traffic.
|
From page 5... ...
Chapter 1/Introduction Page 1-5 Roundabouts: An Informational Guide 2. Rotaries (see Exhibit 1-3)
|
From page 6... ...
Roundabouts: An Informational Guide Page 1-6 Chapter 1/Introduction include raised channelization to guide the approaching driver onto the circulatory roadway. At some traffic circles, left-turning movements for larger vehicles are allowed to occur in front of the central island, potentially conflicting with other circulating traffic.
|
From page 7... ...
Chapter 1/Introduction Page 1-7 Roundabouts: An Informational Guide Exhibit 1-6 provides two examples of intersections that were converted to modern roundabouts from older rotary designs. The Long Beach, California, example retains the original diameter of the rotary but improves the design of the entries.
|
From page 8... ...
Roundabouts: An Informational Guide Page 1-8 Chapter 1/Introduction Therefore, the ability to carefully distinguish roundabouts from other circular intersections is important. 1.2.2 COMPARISON OF FEATURES BETWEEN ROUNDABOUTS AND OTHER CIRCULAR INTERSECTIONS Exhibit 1-7 identifies some of the major characteristics of roundabouts and contrasts them with other circular intersections.
|
From page 9... ...
Chapter 1/Introduction Page 1-9 Roundabouts: An Informational Guide Roundabouts Traffic Circles Traffic Control Yield control is used on all entries. The circulatory roadway has no control.
|
From page 10... ...
Roundabouts: An Informational Guide Page 1-10 Chapter 1/Introduction 1.3 CATEGORIES OF ROUNDABOUTS For the purposes of this guide, roundabouts have been separated into three basic categories according to size and number of lanes to facilitate discussion of specific performance or design issues: mini-roundabouts, single-lane roundabouts, and multilane roundabouts. Note that separate categories have not been explicitly identified for rural, urban, and suburban areas.
|
From page 11... ...
Chapter 1/Introduction Page 1-11 Roundabouts: An Informational Guide inscribed circle diameters due to smaller design vehicles and existing right-of-way constraints. They may also include more extensive pedestrian and bicycle features.
|
From page 12... ...
Roundabouts: An Informational Guide Page 1-12 Chapter 1/Introduction In most cases, roundabouts in all three categories are designed with pedestrian and bicycle facilities; however, in some instances a jurisdiction may choose to not provide these features if these types of users are not anticipated or can be better served in another location. 1.3.1 MINI-ROUNDABOUTS Mini-roundabouts are small roundabouts with a fully traversable central island.
|
From page 13... ...
Chapter 1/Introduction Page 1-13 Roundabouts: An Informational Guide is precluded by right-of-way constraints. In retrofit applications, mini-roundabouts are relatively inexpensive because they typically require minimal additional pavement at the intersecting roads and minor widening at the corner curbs.
|
From page 14... ...
Roundabouts: An Informational Guide Page 1-14 Chapter 1/Introduction Exhibit 1-12 Features of Typical SingleLane Roundabout Exhibit 1-13 Examples of Single-Lane Roundabouts (a) Dublin, Ohio (b)
|
From page 15... ...
Chapter 1/Introduction Page 1-15 Roundabouts: An Informational Guide more approaches (e.g., two-lane entries on the major street and one-lane entries on the minor street)
|
From page 16... ...
Roundabouts: An Informational Guide Page 1-16 Chapter 1/Introduction (a) Bend, Oregon (b)
|
From page 17... ...
Chapter 1/Introduction Page 1-17 Roundabouts: An Informational Guide 1.4 SCOPE OF THE GUIDE This guide provides information and guidance on roundabouts, resulting in designs that are suitable for a variety of typical conditions in the United States. The scope of this guide is to provide general information, planning techniques, evaluation procedures for assessing operational and safety performance, design guidelines for roundabouts, and principles to be considered for selecting and designing roundabouts.
|
From page 18... ...
Roundabouts: An Informational Guide Page 1-18 Chapter 1/Introduction roundabouts from other circular intersections and defines the types of roundabouts addressed in the remainder of the guide. The remaining chapters in this guide increase in the level of detail provided.
|
From page 19... ...
Chapter 1/Introduction Page 1-19 Roundabouts: An Informational Guide 1.6 REFERENCES 1. Brown, M
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.