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I-193 (numbered as another interstate) New Hampshire
I-293 New Hampshire
11.18 miles ; western loop of I-93 in Manchester. The vertical section of Interstate 293 follows the Everett Turnpike, though tolls are waived in that area.
See also: I-293 photos (Alexander R Svirsky)
I-393 New Hampshire
4.60 miles ; spur off I-93 to the east in Concord.
The original section, built around 1979, used to end at a T intersection with US 4/202 and NH 9, about a mile west of NH 106.
Construction on the extension toward Chichester lasted from 1985-1988. In 1992, routes 4/202/9 were widened to three lanes from the end of I-393 to Epsom Circle at NH 28, probably indicating that there are no plans to extend Interstate 393 further. 
See also: I-393 photos (Alexander R Svirsky)