Sub-problem 3c: The Southwestern Quadrant

Step 1. Setup

The semi-direct ramp from Route 7 WB to I-787 SB starts at the west end of the bridge across the Hudson. (See the discussion about the weaving movement at Location B in Sub-problem 3a.) The two lanes from the weaving movement at Location B diverge to the north then swing south in a large-radius, counterclockwise curve. Within a tenth of a mile, a new lane is added on the right that becomes the right-hand exit ramp to I-787 north. The original two lanes continue, merging into one lane, passing underneath Route 7, and merging with both I-787 south and the right-hand ramp coming from Route 7 east. The speed on the semi-direct ramp is 40 mph.

The connection from Route 7 EB to I-787 SB starts with the right-hand exit ramp on Route 7 EB. No deceleration lane is provided. The exit is immediate, like a slip lane. About 150 feet further, the single lane expands to two. The new lane, added on the left, becomes the collector/distributor road while the old lane, continuing straight ahead, veers to the right and becomes the right-hand ramp leading to I-787 SB. The curve on the ramp is sharp and is limited to 30 mph. Another 1,580 feet later, the ramp begins paralleling the semi-direct ramp from Route 7WB. The two continue side-by-side for about another 1580 feet before they merge. After the merge, they continue southbound for another 400 feet then merge with I-787 SB.

During the AM peak hour, the ramp from Route 7 EB to I-787 SB often produces a queue stretching half-way back to I-87. In Sub-problem 3b, we found that the section of roadway on the ramp from Route 7 EB to I-787 SB is at or near capacity. See Exhibit 4-58. To learn more about why this ramp might be a problem, we start the analysis by studying the diverge from Route 7EB and move south through the complex toward the I-787 SB merge.