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Sub-problem 4a - Page 2 of 5

ID# C204A02

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

Lane Utilization
Lane utilization is an important issue on all four approaches. In the case of the eastbound approach, the I-87 southbound on-ramp is immediately downstream of the intersection. The right-hand-most through lane is used far more than the other two. Thereís a secondary impact for drivers wanting to turn right who canít get into the auxiliary right-turn lane because the long queue blocks access. For the westbound approach, the double left has unbalanced lane use. The innermost lane is sometimes blocked by the outer one. Traffic tends to use the outer lane because it leads to the Shoppers World Plaza and some convenience stores. In the case of the northbound approach, the double left has balanced lane use. The right-most lane leads to stores on the north side of Route 146 just west of the intersection, but there are also drivers who want to continue west, so both lanes see substantial use. For the southbound approach, the lane use is not necessarily unbalanced, but the lane use designations are complex (left, left/through, and through/right). We will study that approach separately.

Exhibit 2-40 shows the differences between including and not including lane utilization. The utilization values employed by movement are shown in the bottom line of the table. In Dataset 32 (the base case) and Dataset 33 (no lane utilization) the impact is substantial for the eastbound throughs. With the lane utilization included, that movement has a delay of 28.6 seconds per vehicle. Without it, the delay is only 22.5 seconds per vehicle, a 27% difference.

Exhibit 2-40. Clifton Country Road Effects of Lane Utilization
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 0.03 0.81 0.24 - 0.53 0.73 - - 0.41 0.20 0.34 - 0.40 0.21 - -
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 33 No Lane Utilization Delay 34.5 22.5 10.2 20.5 30.9 19.6 12.9 22.4 33.2 32.0 33.2 33.0 32.3 31.2 32.0 23.4
v/c 0.03 0.57 0.24 - 0.51 0.68 - - 0.42 0.20 0.34 - 0.40 0.21 - -
95-Queue 0.2 13.1 5.3 - 6.9 19.1 - - 4.4 2.2 3.2 - 4.4 2.5 - -
Queue 0.1 6.8 2.6 - 3.4 10.4 - - 2.2 1.1 1.6 - 2.2 1.2 - -
 
Observed Lane Utilization 1.00 0.67 1.00 - 0.91 0.88 1.00 - 0.97 1.00 1.00 - 1.00 0.95 -

*Using an 82-second cycle length during the a.m. peak hour

The differences for the other movements arenít as remarkable, because the lane utilization values are closer to the defaults. The defaults are 1.0 for single lanes and 0.95 for double lanes. In the case of the northbound left, the delay in the base case is actually lower than in the no utilization situation because the observed lane utilization is higher than would have been assumed by default.

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