I-790  New York (link)

2.41 miles [1]; odd L-shaped freeway in Utica; parallels I-90 for 1.5 miles before going south with NY 5 and 12. Dates back to 1965 or earlier.

The road is reportedly barely noticeable these days around Utica as I-790 -- there are a few trailblazers for it, but no I-790 reassurance markers on the highway itself. [2] Most locals refer to it as Routes 5, 8, and 12, or "the arterial." [3]

J. P. Wing elaborated on the signing situation [4]:

• Number of signs for I-790 west on the Thruway: 3
• Number on I-790 itself: 0
• Number of signs for I-790 east: a few
• Number of I-790 signs on the 5/8/12 overlap: 0

Furthermore, based on its reference markers, I-790 actually has four ends, not two (ASCII art by J. P. Wing):

        |
     ---+---------
        |
        |
        |

See a 790 trailblazer photo at J. P. Wing's Photo Gallery.

Sources

1. Route Log and Finder List - Interstate Highways, FHWA, Oct. 31, 2002.
2. Wing, J. P. (New York US and Interstate Routes)
3. Naughton, Peter. '3di's.' Personal email, Nov. 2, 2000.
4. Wing, J. P. 'Fixing I-790.' Post to misc.transport.road, March 23, 2002.