Problem 2 - Page 1 of 2
Problem 2: Operational
analysis of the I-87/Alternate Route 7 Interchange
This problem focuses on the interchange
complex on the western end of Alternate Route 7. Three interchanges are
intertwined: I-87 and Alternate Route 7, I-87 and State Route 2, and Alternate Route 7 and U.S. 9. Click the thumbnails
Exhibit 4-17 and
Exhibit 4-18 for a visual introduction to this problem. Before proceeding with this problem, we first provide more details on the
interchange geometry below.
The interchange between I-87 and Alternate Route 7 is a
classic trumpet with the semi-direct ramp linking Alternate Route 7 west to I-87
south. Locally, itís called Exit 7, as noted in
Exhibit 4-18. The one nuance worth
noting is that the right-hand ramp from Alternate Route 7 west to I-87 north
leaves Alternate Route 7 east of
U.S. 9 and
follows a fairly long path on its way to I-87 north.
The Alternate Route 7/U.S. 9 interchange is a
partial-cloverleaf. The connections to Alternate Route 7 east are on the eastern
side of U.S. 9 while the connections to Alternate Route 7 west are on the
western side. An extra ramp is needed to provide the connections, because the
right-hand ramp from Alternate Route 7 to I-87 starts east of the bridge under
U.S. 9, before the ramps from U.S. 9 connect to Alternate Route 7. Consequently,
to provide connection from U.S. 9 via Alternate Route 7 to I-87, an extra ramp
diverges from the U.S. 9 on-ramp north of NYS-7 and connects directly to the
right-hand ramp from Alternate Route 7 west to I-87 north.
The interchange between I-87 and State Route 2, Exit 6, is a simple diamond.
Itís called Exit 6 as labeled in the diagram. Getting to it coming southbound is
a bit complex. That needs a short discussion.
] to Problem 1 [ Continue ]
with Problem 2