Sub-problem 3b - Page 1 of 10
Step 1. Setup
This sub-problem focuses on some basic issues in ramp
analysis. As you already know, the ramps not the intersecting freeways or
the arterials create the most common capacity constraints at interchanges.
Ramps that work well are crucial to good performance at an interchange, so
they demand considerable attention during construction, reconstruction, or
Since this case study focuses on the analysis of freeways,
considerable attention has been devoted to ramp-related issues.
Ramp-related topics are discussed in Problem 2 Sub-problems 3b, 3c, and 3d.
In this sub-problem, we deal with ramp issues that are relatively simple. In
sub-problems 3c and 3d, we address more complex problems, involving
situations that donít follow a standard for a ramp analysis.
Sub-problem 3a also focuses on ramp-related issues. The
discussion about the weaving section for Location E starts with the end of
the ramp from Route 7 east to I-787 north and ends with the beginning of
the ramp from I-787 north to Route 7 west. So weaving sections are sometimes
part of a ramp analysis.
Deciding what analyses to do for a given ramp takes some
Since the HCM doesnít provide a single point of contact to
deal with the total spectrum of ramp related analyses,
You might need as many as four methodologies to completely analyze
a set of ramps at a given interchange: weaving sections, merge and diverge
locations, unsignalized intersections, and signalized intersections.
Every ramp has
three sections: a beginning, middle, and end or terminus. If you study all
three, you have completely studied the ramp. We need to discuss how you
analyze each of these sections and how the HCM ramp chapter fits in.
Consider the following questions: