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Orientation: Interstate 481 runs top to bottom, while Interstate 690 enters at left, ending at Interstate 481. A corner of the Village of East Syracuse is at top left. Butternut Drive is the surface road at lower right.
Exit numbers: This interchange is Exit 4 for I-481. It is not a numbered exit for I-690, being its terminus.
The interchange: This is a four-way interchange at a three-way junction. An extension of I-690, considered a replacement for NY 5, was planned to run east from this point to Chittenango. In anticipation of this, a full interchange was constructed, although the planned highway, after being truncated to Manlius Center, was cancelled in the late 1980's.
The interchange is an early Interstate-era design, similar to the interchange between Interstates 390 and 490 at Rochester, featuring spread medians and left-hand exit ramps. Remarkably, all of the unused ramps and overpasses are visible in this photograph, including a short stub at bottom right that would have provided the northbound-to-eastbound connection. The eastbound through roadway ends between I-481 and Butternut Drive, and connects to the westbound roadway through the grounds of an industrial facility on Butternut Drive. Most of the unused ramps have full acceleration/deceleration lanes, but are separated from the useable lanes by concrete barriers. The most prominent of the "ghost" ramps is the loop at the northwest corner; this is often mistakenly shown on street-level maps as a viable roadway.
As it exists today, the interchange happens to assume a
directional-T design, except that the northbound entrance and exit
ramps cross in the median of I-481, rather than at a three-level
crossing with the southbound roadway, as is usual for this design.
Additional info from Doug Kerr