Problem 2 - Page 2 of 2
Problem 2: Operational analysis of the I-87/Alternate Route 7 Interchange
Looking again at
Exhibit 4-18, you can see that all southbound vehicles wanting either Exit 6 or Exit 7 have
to leave I-87 at the top of the diagram. Those going to Alternate Route 7 east diverge where the loop ramp turns west. Those going to Exit 6
continue south. Vehicles coming south
from I-87 toward Exit 6 weave through the vehicles from the semi-direct
ramp to I-87 south. A high percentage of vehicles on
the semi-direct ramp have to cross the
I-87 traffic going to Exit 6 then use the single lane slip ramp south of Location C to get to I-87. This
difficult weave is one of the places analyzed in this problem.
Now that you know some important details on the geometry of
the interchange, let's consider the problem at hand, the completion of an operational
analysis of the interchange. We will consider two specific
procedures from the HCM, one to analyze weaving sections and the other to
analyze ramp junctions. We will illustrate these two procedures using the four
sub-problems listed below.
Sub-problem 2a. What
types of analysis should be conducted on the I-87/Alternate Route 7 interchange?
Sub-problem 2b. What are the
levels of service in the weaving sections located in the I-87/Alternate Route 7 interchange? These sections are
noted as points A, B, and C in the interchange sketch.
Sub-problem 2c.What are
the levels of service along the ramp and at the ramp junction for the on-ramp
from Alternate Route 7 to I-87 northbound?
This section is noted as point D in the intersection sketch.
What is the effect of making
geometric improvements to the
ramp and at the ramp junction for the on-ramp from Alternate Route 7 to I-87
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