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Understanding Roundabouts
Vincent Reynolds, P.E.
Overview
Traffic circles have been used in the
U.S. since 1905. The modern roundabout, developed in the United
Kingdom, was developed to rectify problems associated with traffic circles. This
course will provide information that will guide the engineer in planning,
designing and constructing several types of roundabouts. Several traffic
scenarios will be provided along with information to get a solution. This 10
hour course will also discuss the safety and operational characteristics of
roundabouts and give crash statistics that will educate the reader on the
positive effects of utilizing roundabouts.
The course materials
are based solely on the materials “Roundabouts: An Informational Guide” as
published on the website of the FHWA’s Turner – Fairbank Highway Research
Center.
The student must take a multiple-choice quiz consisting of forty-seven (47) questions
at the end of the course to obtain PDH credits.
Specific Knowledge or Skill Attained
This course teaches the following specific knowledge and
skills:
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How traffic circles are used in the U.S.
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Why roundabouts were developed
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Key features of a roundabout
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Speed designs for roundabouts
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Geometric layout of roundabouts
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Required traffic markings for roundabouts
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How pedestrians and bicycle traffic fit into
roundabout design
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How to compare the cost of roundabouts to
signalized intersections
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The economies related to roundabout design
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How to perform a benefit cost ratio for a build
or no-build condition
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How to design a roundabout to operate
effectively with the current AADT
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The environmental impacts of roundabouts
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The capacity of roundabouts and their effects on
traffic
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How to determine the required queue length based
on traffic volume.
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The three key performances that should be known
when designing a roundabout
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The number of conflict points in a conventional
intersection.
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The number of conflict points in a roundabout
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Why roundabouts have less conflict points than
conventional intersections
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Cross slopes in roundabouts
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How central islands play a role in roundabouts
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Typical pavement markings for roundabouts
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How to design a lighting plan for roundabouts
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How public meetings play a role in roundabout
design
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What raindrop islands are and how they are used
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The side friction factor for various speeds
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Steps to plan roundabouts
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Maximum service volumes for roundabouts
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How esthetics are considered at roundabouts
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The relation between traffic delay and the
environment
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How roundabouts can reduce red-light running by
eliminating the traffic signal, (Refer to the PDHengineer.com Course C-8004
Countermeasures to Reduce Red-Light Running for more in-depth and interesting
information about red-light running that every driver should know)
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Required data to evaluate a roundabout
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Most importantly, how
the public will benefit from safer intersections and roadways
Course
Click on the following PDF attachment(s) and review the document “Roundabouts:
An Informational Guide”
prior to taking a quiz for credit.
Download Entire Document
Entire Document (4.3 MB)
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To obtain PDH credits for this course, you will need to take a quiz for
credit. Click on the link below.
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