Sub-problem 3a: Weaving Analysis

Weaving Segment C

Location C is the next place to study. The inbound facilities are I-787 northbound (3 lanes) and the 23^rd Street northbound on-ramp (one lane). The outbound facilities are I-787 northbound (two lanes) and the Route 7 eastbound off-ramp (two lanes). This is a Type C weave, because traffic from the 23^rd street on-ramp has to shift left at least two lanes to reach I-787 north. The on-ramp becomes the outer lane of the Route 7 east off-ramp, and the third lane on I-787 becomes the inner lane of the exit ramp. The weaving section is about 1,000 feet long.

This weaving section shows how the distribution of flow among weaving and non-weaving movements can affect the facility’s performance. The PM peak hour volumes are larger, so we’ll use them for the analysis.

The PM peak hour volumes for the traffic entering and exiting the weave are shown in Exhibit 4-48. Please note our data don’t include the distribution of flows through the weaving segment. This is common. It’s hard to get the actual weaving volumes in the field. You have to track many individual vehicles through the facility to get an accurate sense of the distribution of the flows (i.e., AC, AD, BC, and BD, in Exhibit 4-49.) Because of the hours required for this process, it is common to have to estimate these volumes and then conduct a sensitivity analysis to determine the validity of these estimates.