Sub-problem 3c - Page 2 of 4 |
ID# C103C02 |
Sub-problem 3c: Critical movement analysis
What is critical movement analysis? Critical
movement analysis is a method to determine whether the projected volumes at a
signalized intersection will be under, near, or over the intersection's capacity
to accommodate them. The method is fully documented as a planning-level
procedure in Transportation Research Circular 212. The method considers each of the
four conflicting movement pairs at the intersection (for example, the NB LT and
the SB TH movements). The critical movements for each intersection phase
(for example, the maximum of either the NB LT/SB TH movement and the SB LT/NB TH
movement) are summed. This sum is compared with the following standards:
Exhibit 1-36. Intersection Performance Assessment by
Critical Volume |
Sum
of Critical Volumes (v/hr) |
Intersection Performance Assessment |
0-1,200 |
Under capacity |
1,201 - 1,400 |
Near capacity |
1,401 and above |
Over capacity |
What data are needed to conduct critical movement
analysis? The approach volumes, the number of lanes, and the lane
configuration on each approach are the data
needed to conduct a critical movement analysis.
What outputs are produced by critical movement analysis? Critical movement analysis produces only
an assessment of the intersection's sufficiency to accommodate the projected
volumes. It does NOT provide estimates of delay, LOS, or queue lengths.
Are the results from critical movement analysis any more or
less valid than the results produced by the HCM or by microscopic simulation
models? The results of a critical movement analysis help to determine
whether the intersection will operate under, near, or over capacity. It is
more of an approximation than either the HCM or other models, but in many cases
the results from a critical movement analysis are sufficient to answer the
question at hand.
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