A
wrong-way multiplex occurs when two or more roads become one physical road and two routes are signed in opposite directions. For example,
Interstate 93 is multiplexed with
Massachusetts State Highway 128 near Boston, but I-93 northbound is signed as going the same direction as MA-128 southbound and vice versa. At the multiplex of
Interstate 77 and
Interstate 81 in Virginia, I-77 northbound is signed as I-81 southbound and vice versa.
See also multiplex.