Overview - Page 1 of 1
Printable Overview, Introduction, and Getting Started
This case study presents information on a decision that will
be made by the Idaho Transportation Department regarding the operation of an
intersection on U.S. Highway 95 within the City of Moscow, Idaho. The
intersection is currently stop-sign controlled but consideration is being given
to installing a traffic signal at the intersection. Click here to
see what kinds of problems will be considered as part of this case study.
The case study includes six problems, each one illustrating
some aspect of this decision:
Problem 1 analyzes the intersection under both stop sign and signal control;
Problem 2 addresses the effects of
adjacent intersections as well as progression considerations;
Problem 3 illustrates how to
evaluate the intersection under oversaturated conditions, and also how to
take account of a significant change in vehicle mix;
Problem 4 addresses the issue of
Problem 5 suggests how to deal with
an adjacent road segment that is neither an arterial nor a two-lane highway;
Problem 6 shows how a
planning-level analysis might be conducted.
The purpose of each of the problems is to
show how various traffic analysis tools that are contained in the
Capacity Manual can be applied to assist traffic analysts, engineers, planners
and decision-makers in making sound investment decisions regarding the
signalization decision. There are some situations where this amount of analysis
would not be necessary in order to make an informed decision, but the issues
presented herein should always be considered so as to assure the final decision
is consistent with system performance objectives.
The problems in this case study focus on the chapters of the
HCM that deal with interrupted flow facilities, either signalized or
unsignalized intersections. After studying this material, you should be
Analyze the operation of signalized intersections,
unsignalized intersections, and urban arterials using the HCM.
Understand what input data are required and the
assumptions that are commonly made regarding default values for the HCM
procedures for these facilities.
Know the appropriate kinds of analysis that should be
undertaken for both existing facilities as well as future facilities or conditions, including the scope of a facility that should be included
in an analysis.
Understand the limitations of the HCM procedures and
when it is appropriate to use other models or computational tools.
Know how to reasonably interpret the results from an
HCM analysis and how these results can be used to support a particular
decision regarding a change to a transportation system.
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