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Subproblem 6b - Page 2 of 3 |
ID# C306B02 |
Sub-problem 6b:
Consideration of a Grade-Separated Flyover
What
additional data should be gathered to determine whether grade separation
is appropriate? In this
limited review of the intersection we have only completed an analyses of
questions related to capacity and performance for the peak hour.
Justification for a grade-separated flyover must consider the traffic
conditions during other hours of the day. Other data such as crash history
should be gathered to determine the extent that safety considerations can
justify the construction of the facility. Finally, other users such as
pedestrians and cyclists should also be considered to determine the extent
that a grade-separated flyover affects the connectivity and safety of
these modes.
What conflicting movements might benefit from grade
separation?
There are three crossing
conflict points associated with this intersection:
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EB through (2,010 vph) vs. NB left (257 vph) |
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EB through (2,010 vph) vs. WB left (120 vph) |
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NB left (257 vph) vs. WB left (120 vph) |
The most critical conflict clearly involves the eastbound through vs.
northbound left-turn movements. A grade-separated flyover for the northbound
traffic would eliminate this conflict as well as the conflict between the
northbound left-turn and westbound left-turn movements. It would also convert
the conflict between the northbound left and westbound through traffic from
a crossing conflict to a merging conflict. Recognizing that other
grade-separated interchange configurations are possible, we will use the
northbound flyover in this sub-problem to illustrate the use of the HCM in
assessing the benefits of a proposed grade separation.
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