Interchange of the Week
Monday, 17 September 2001
New York State Thruway - Exits 21, 21B and 21A, Catskill-Ravena
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Exit 21

Orientation: The New York State Thruway (Interstate 87) runs from left to top right. NY 23 runs from left to right at bottom, and Greene CR 23B runs from top to bottom.

Exit numbers: Exit 21 on the New York State Thruway is for NY 23 to Catskill and Hudson.

The interchange: The "trumpet" interchange at Exit 21 connects not to NY 23 directly, but instead to CR 23B. However, this road (which is actually reference route 911V between NY 23 and the Thruway interchange) is the former alignment of NY 23, and carried the designation at the time the Thruway was built. Since then, NY 23 has been rerouted onto a new expressway intersecting CR 23B at a diamond interchange, also visible in the photo.

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Exit 21B

Orientation: The Thruway runs from bottom to top, while US 9W runs across the top left corner.

Exit numbers: Exit 21B is for US 9W to Coxsackie.

The interchange: This interchange shows a variation of the "trumpet" design used when the intersecting roadway is parallel, rather than perpendicular, to the main highway. This exit is newer than both Exit 21 and Exit 21A, and as it lies between the two, it is somewhat out of order in the Thruway's exit numbering scheme. The interchange is located a short distance north of the Village of Coxsackie, where US 9W intersects NY 81 and NY 385.

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Exit 20

Orientation: The Thruway mainline runs from bottom to top. The Berkshire Section (reference route 912M) of the Thruway runs toward the right. NY 144 runs close by the Thruway on the right-hand side.

Exit numbers: Exit 21A is for the Massachusetts Turnpike to Boston.

The interchange: The Berkshire Section of the New York State Thruway runs from Exit 21A on the mainline to the Massachusetts state line, where it becomes the Massachusetts Turnpike. The interchange here has the usual "trumpet" configuration, although it is so constructed as to allow high-speed connections between points north and east, hence its elongated profile. Note also that all of the ramps have enough width of pavement for two lanes of traffic, although only the southbound-to-eastbound ramp is marked for two. Within the interchange passes a branch of the CSX Transportation railroad, connecting freight yards at Selkirk with the mainlines to New York and Boston on the east side of the Hudson River.

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Castleton-on-Hudson Bridge: The northernmost toll crossing of the Hudson River is the Castleton-on-Hudson Bridge, on the Berkshire Section of the Thruway just east of Exit 21A. A railroad trestle runs along the south side of the Thruway bridge, carrying occasional freight traffic between lines on either side of the river. To the south of the railroad a set of high-tension power lines also spans the river. The Thruway bridge consists of a cantilevered section over the river's main channel, along with one short and one longer continuous truss segment. Besides the Hudson itself, this bridge also spans two smaller tributaries, a section of Schodack Island State Park and its access road, the CSX Transportation mainline on the east shore, and NY 9J.

New York State Thruway Authority official site.

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