Sub-problem 3a: Weaving Analysis

Weaving Segment E
The weaving segment at location E is three lanes wide and a Type A weave. It is located on I-787 north between the on-ramp from Route 7 east and the off-ramp to Route 7 west. It has a relatively short weaving length (790 feet) and heavy PM peak hour volumes.

In this case, the weaving movement volumes (AB, AC, BC, and BD) are easy to determine, because very few if any of the vehicles coming from the on-ramp will want to go to the off-ramp. We can assume the volume from the on-ramp to the off-ramp will be zero. That means all of the on-ramp traffic goes to I-787 north and all of the off-ramp volume comes from I-787 north.

To complete the data inputs, we’re going to assume 1) that the free flow speed on the freeway is 55 mph, 2) the speed on the on- and off-ramps is 25 mph, and 3) the peak hour factor is 1.0. The latter assumption means the volumes will be identical for all four 15-minute periods during the peak hour for all four weaving movements.

The volume ratio (VR) in the AM and PM peaks exceeds 0.45, indicating the weaving volumes are more than 45% of the total volume. This indicates that most of the traffic coming from I-787 north goes to Route 7 west. None of the traffic from the on-ramp goes to the off-ramp. It all goes to I-787 north. The HCM cautions to not trust the HCM predictions if the volume ratio exceeds this value. So it is important to look closely at the results we get.

We’ll examine both the AM and PM peaks. The results are shown in Exhibit 4-53 . As you might expect, the LOS for the PM peak is much worse than the AM peak, because the PM volumes are twice the AM volumes. In fact, the HCM predicts LOS is F in the PM Peak.