Problem 1: Basic Freeway Sections

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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?

Discussion:
Take a few minutes to consider these questions. When you are ready to continue, click continue below to proceed.