Problem 1 - Page 1 of 2
Problem 1: Basic Freeway
sections are among the most elementary of all highway facilities. They are
single-directional links that tie one freeway juncture to the next. The
freeway junctures can be weaving sections, ramp junctions, or merge or
diverge points. Basic freeway sections are quickly identifiable because
there is no distinctive pattern to the lane changing, and no evidence exists of
distinctive subordinate traffic streams, as there would be at a weave, a
ramp, or a merge or diverge.
In this case study, two basic freeway sections exist on Route 7 between I-87
and I-787, both eastbound and westbound as shown in
Exhibit 4-3. The basic
freeway sections are approximately three miles in length and each direction
has characteristics that are unique.
The eastbound AADT is about 29,700 and the peak hour
volumes range up to about 3,250 in the AM peak and 2,400
in the PM peak.
The westbound section has an AADT of about 30,000 vehicles and peak hour volumes
of approximately 2,400 veh/hr in the AM peak and 3,500
in the PM Peak.
In this problem,
we'll use both of these directions to provide illustrations of a basic
freeway analyses. The eastbound direction
is fairly basic and will allow us to get familiar
with the input variables and the outputs, and to see how changes in some of
those variables influence the results. The
westbound direction has some distinct characteristics
that will allow us to look at issues related to the number of lanes
available, the designation of truck climbing lanes, and grades.
Here are some points to consider as you read through problem 1:
What time periods do you think should be selected for
doing an analysis of a basic freeway section?
What are the two or three most important characteristics of this subarea
that will likely define the operational performance of these basic freeway
sections? Do the defining characteristics differ by direction? How is the
configuration of each basic freeway section likely to affect downstream
system elements like merge points, diverge points, and weaving areas?
a few minutes to consider these questions. When you are ready to
continue, click continue below to proceed.
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