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Sub-problem 4a - Page 5 of 5

ID# C204A05

Sub-problem 4a: Clifton Country Road AM peak hour - Existing Conditions

Exhibit 2-42. Clifton Country Road Effects of Lane Group Treatments for the Southbound Approach
Condition* Performance Measure Eastbound Westbound Northbound Southbound OA
L T R Tot L T R Tot L T R Tot L T R Tot
Dataset 32 Base Case Delay 34.5 28.6 10.2 25.6 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 32.3 31.2 32.0 25.9
v/c ratio 0.03 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 0.2 - -
95-Queue 0.2 15.6 5.3 - 6.9 20.0 - - 4.4 2.2 3.2 - 4.4 2.5 - -
Queue 0.1 8.3 2.6 - 3.5 11.0 - - 2.1 1.1 1.6 - 2.2 1.2 - -
Dataset 36 Single SB Lane Group Delay 34.5 28.6 10.2 25.6 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 31.8 31.8 25.9
v/c ratio 0.0 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.4 - -
95-Queue 0.2 15.6 5.3 - 6.9 20.0 - - 4.4 2.2 3.2 - 3.8 - -
Queue 0.1 8.3 2.6 - 3.5 11.0 - - 2.1 1.1 1.6 - 1.8 - -
Dataset 37 SB Grouping as L, LT, TR Delay 34.5 28.6 10.2 25.6 31.3 21.0 12.9 23.4 33.1 32.0 33.2 33.0 49.9 30.5 45.4 26.6
v/c ratio 0.0 0.8 0.2 - 0.5 0.7 - - 0.4 0.2 0.3 - 0.8 0.1 - -
95-Queue 0.0 15.6 5.3 - 6.9 20.0 - - 4.4 2.2 3.2 - 10.1 1.2 - -
Queue 0.1 8.3 2.6 - 3.5 11.0 - - 2.1 1.1 1.6 - 5.2 0.6 - -

*Using an 82.0 second cycle length during the a.m. peak hour

You can also group all the movements together and have a generic 3-lane approach (Dataset 36). That produces the Single SB Group results shown in Exhibit 2-42. The results aren’t significantly different from those in the base case, but the distinction is lost between the innermost two lanes and the outer lane.

You could also create a scenario that looks like field observations: a single left-turn lane, two lanes assigned partially to through movements, and shared lefts and rights (Dataset 37). However, this produces a result that is very different from the base case, as seen in the third scenario in the table. The delays for the southbound left are quite large, 49.9 seconds per vehicle, and the queue length values are two-and-a-half times those of the base case. This lane grouping definition doesn’t match the field conditions.

We have identified a way to model the situation that matches the behavior that’s been observed in the field. In this case, the base case or the single SB lane group seems best.

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