Back Continue

Getting Started
Problem 1
Problem 2
Problem 3
Problem 4
Problem 5
Problem 6
Problem Index


Sub-problem 5c - Page 3 of 3

ID# C205C03

Sub-problem 5: I-87 Interchange - Stop and Yield Controlled Junctions

Westbound Entrance to the Southbound On-Ramp
People sometimes forget that interchanges break down into an inter-related set of more discrete facilities. The ramp termini are a good example. The westbound left on Route 146 that leads to the southbound on-ramp is an unsignalized intersection. The westbound, left-turning traffic has to cross the oncoming eastbound through traffic to enter the on-ramp.

To see how well this location is performing and how well it might perform in the future, we did a set of unsignalized intersection analyses (Datasets 74-78). Exhibit 2-63 presents the results. The findings are discouraging. In the existing AM peak, the performance is okay, as are the AM Without and AM With conditions in the future. However, in the PM Existing conditions, the table reflects what can be observed anecdotally. The delays for the westbound left turn can be long, and there often is a queue at that location. The table further projects that the PM Without condition will be worse as will the PM With. The 95th percentile queue of almost 7 vehicles can be accommodated; the left turn bay is quite long. However, the delays are considerable and some mitigation may be needed. A signal is the logical choice, but it may not be necessary. The left turn tends to operate in the shadow of the Clifton Country Road intersection. There are lulls in the westbound traffic because of the traffic light, and Exhibit 2-63 may be overstating the delays, enough that acceptable operation in the PM With condition may still be feasible and reasonable. 

Exhibit 2-63. I-87 Interchange Performance of the Westbound
Left-Turn Entrance to the Southbound On-Ramp


Delay v/c 95% Queue LOS
AM Existing 11.7 0.45 2.42 B
AM Without/With 12.1 0.48 2.69 B
PM Existing 26.7 0.66 4.66 D
PM Without 31.8 0.72 5.64 D
PM With 42.0 0.80 6.98 E

  Back ] Continue ] to Discussion