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Orientation: Interstate 490 runs from left center, where it crosses the Genesee River on the Troup-Howell Bridge, to bottom right. Rochester's Inner Loop* branches from I-490 to right center. South Clinton Avenue runs bottom to top at center. One block east is Chestnut Street, which becomes Monroe Avenue at the Inner Loop overpass. South Avenue runs bottom to top at left, coming to a dead end on either side of the interchange but connected by ramps running through it. Woodbury Boulevard runs left to right at top.
NY 15 enters on Mount Hope Avenue (diagonal at bottom left). Northbound traffic continues across South Avenue onto Byron Street, then turns left onto one-way South Clinton Avenue. NY 15 ends at Woodbury Boulevard (NY 31). Southbound, NY 15 begins at the split of ramps from South Avenue at top left. It continues through the interchange and onto a short stretch of South Avenue before joining its northbound counterpart on Mount Hope Avenue.
NY 31 eastbound enters on one-way South Avenue at upper left, turning onto Woodbury Boulevard just past the ramp split. It continues two blocks to Chestnut Street, and exits at right on Monroe Avenue. Westbound, NY 31 leaves Woodbury Boulevard at South Clinton Avenue, then turns left onto East Broad Street (one block north of photo). It rejoins eastbound traffic at South Avenue.
Exit numbers: On I-490, Exit 16 consists of the single westbound ramp to South Clinton Avenue. Exit 15, an eastbound-only exit, is for the Inner Loop and South Avenue (NY 15). Entrance ramps from the Inner Loop may also be considered part of Interchange 15, while those from South Avenue are functionally more complementary to Exit 16.
The interchange: A very unusual feature here is the existence of two ramps from the Inner Loop, each also joined by a ramp from South Avenue, that both connect to I-490 eastbound. The first forms a tight loop just west of South Clinton Avenue, then dips under the Inner Loop and over I-490. It then makes another loop at the corner of Byron Street and South Clinton Avenue (to which corner there is also a connection), where it is joined by the ramp from South Avenue before connecting to I-490 on the right-hand side. (This ramp, as part of the Troup-Howell Bridge reconstruction, will be realigned to meet Byron Street mid-block, allowing access to I-490 eastbound from points south.) The second ramp begins at a split, where the left lane merges into the Troup-Howell Bridge (the Inner Loop designation continues west along I-490 at this point). The right lane swings onto an elevated loop jutting slightly out over the Genesee River. After being joined by the second ramp from South Avenue, this ramp makes a tight left-hand curve, then joins I-490 from the left, directly opposite the first ramp. This situation stems from the cancellation of the Genesee Expressway (I-390), which was to have its terminus here. The first ramp was originally intended for the southbound Genesee Expressway, which would have run parallel to I-490 between here and Exit 17. The second was always intended for I-490, and today serves as the shorter connection, although both ramps are available from all approaches. This redundancy becomes very useful when the second ramp is closed to traffic every July 4th and January 1st, to be used for the launching of fireworks.
From South Avenue southbound, several ramps branch off. The leftmost lane leads to a left turn to Woodbury Boulevard (NY 31 eastbound), with a dead end shortly beyond. The next lane rises up to join the second ramp described above to I-490 eastbound. The two center lanes carry through traffic for South Avenue and NY 15 southbound (joined by a ramp from I-490 eastbound), and the righmost lanes connect to the first ramp to I-490 eastbound. All of these ramps are also available from Woodbury Boulevard westbound.
Other connections: Also visible here is the first counterclockwise exit on the Inner Loop, to Monroe Avenue and Chestnut Street (NY 31). It is a half-diamond, with the offramp being a named street, Howell Street. It is intersected at its midpoint by Broadway, a residential street. Corresponding ramps forming the other half of this interchange are located just east of this photo.
Missing connections: The most important movement not provided by this interchange is from I-490 westbound to the Inner Loop. Signage directs traffic to Exit 17 (Goodman Street), thence along surface streets to the Inner Loop onramp at South Union Street. However, it is equally practical to remain on I-490 until Exit 13, which is the other end of the Inner Loop, and reach one's destination from the opposite direction.
There is no eastbound exit to South Clinton Avenue, but the Exit 15 ramp to South Avenue fulfills this purpose via Byron Street. Nor are there entrances to I-490 west from any of these streets, but the Inner Loop entrance from Chestnut Street and Monroe Avenue provides the connection. However, commuting patterns at this interchange favor traffic to and from the east. That to and from the west generally uses Exit 13.
Other notes: A new pedestrian overpass (shown here) was constructed east of South Clinton Avenue, to replace a pedestrian underpass that had raised safety concerns. Close inspection of the photo will reveal several other complex sidewalk connections through and amidst the interchange, in particular between the South Avenue and Chestnut Street areas.
An interesting feature visible at extreme upper left is a
grass-covered ramp leading to the intersection of South Avenue and
Court Street. To the right of this is a tunnel entrance. These are both
features of the former interchange point between the Lehigh Valley
terminal yard and the Rochester Subway, which ran under South Avenue at
this point. The Lehigh Valley passenger station still stands and is
visible here; today, it houses a popular restaurant.
*The Inner Loop consists of reference route 940T (three-quarters of a loop around downtown Rochester) and a section of I-490 closing the loop. However, it is practical for our purposes to refer only to the first as the Inner Loop. I-490 has two junctions with reference route 940T, at Exit 13 and Exit 15. This is the eastern of the two.