Currently the
Interstate Highway System includes seven suffixed routes that are signed: the
Interstate 35 split into
Interstate 35E and
Interstate 35W at
Dallas-Fort Worth, Texas; a similar split into
Interstate 35E and
Interstate 35W at
Minneapolis-St. Paul, Minnesota; as well as
Interstate 69C,
Interstate 69E and
Interstate 69W in
South Texas; in addition,
Interstate 480N in Ohio exists and is designated as such on mile markers and exit/entrance ramp signs, but is otherwise unsigned. However, there were once many more, as the
three-digit Interstates were not designated until after all major routes were assigned numbers, including some short connections and spurs. (A few of the shortest, including
I-190 and
I-195, were assigned three-digit numbers almost immediately.) Most were not equal splits like on I-35, but had the main route continue through, and often the suffixed route never returned to its parent. In 1980,
AASHTO abolished the majority of suffixes due to confusion, renumbering them as three-digit Interstates, but several that return to their parents were kept.
Interstate 15E has since become
Interstate 215, but both I-35E/I-35W and I-69 splits still exist.