Unsigned/Secret Interstates

These routes are officially part of the Eisenhower Interstate System. Yet, these routes are official essentially only on paper as no shields or other signage of their existance is posted. They are federally maintained and adhere to the standards of any other signed Interstate highway. In many cases an Interstate is unsigned as to not confuse or overburden motorists with an additional number on an already signed route. This occurs in Maryland with the segment of Interstate 595 as it is already known as U.S. 50 and U.S. 301. See also the Interstates by State index for a state by state list of Interstate Guides.