Interchange of the Week
Monday, 10 September 2001

NY 9A, NY 100, NY 117 & Taconic State Parkway, Pleasantville

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Orientation: The Taconic State Parkway runs from bottom right to top left. Immediately parallel on its left runs the Briarcliff-Peekskill Parkway, carrying the overlapping designations of NY 9A and NY 100. NY 117 runs from left to right, and NY 448 branches from it towards lower left.

The interchange: Just to the north of the Hawthorne complex of interchanges (see Week 49), the Taconic and Briarcliff-Peekskill Parkways run closely parallel for a short distance. Within this stretch, both roadways have an interchange with NY 117. At this junction, both parkways have widened medians, with the result that the northbound Briarcliff-Peekskill and southbound Taconic Parkway lanes are directly adjacent to each other, sharing an underpass with NY 117. This also creates a "wrong-side drive" situation, where opposing traffic streams pass on the left rather than the right (see also Week 2 and Week 47).

The Taconic State Parkway's junction with NY 117 involves only the northbound parkway, where half of a "folded" diamond, or a quarter-cloverleaf, provides the connection. Southbound connections with local roads are somewhat lacking in this area; they are best made just to the north at the Pleasantville Road interchange.

More unusual is the Briarcliff-Peekskill Parkway interchange, a rare interior diamond configuration. In this setup, all entrance and exit ramps fall within the median of the parkway and meet the cross road at a single point between two overpasses. This single intersection is advantageous in congested or high-traffic areas, but the left-hand exit and entrance patterns are considered to be a severe shortcoming. A widely accepted solution to this problem is the Single Point Urban Interchange, or SPUI, an example of which has since appeared on Long Island.

Other connections: There is also an interchange between the two parkways here, consisting of a single ramp from the northbound Taconic to the northbound Briarcliff-Peekskill Parkway. The presence of this ramp eliminates the need to use surface streets at Hawthorne. The other north-to-north movement, from the Briarcliff-Peekskill to the Taconic Parkway, cannot be made at Hawthorne, and so must be made either at Pleasantville Road, or to the south via the Saw Mill River Parkway.