At an intersection with West 55th Street in Summit, IL 171 bends sharply to the north, becoming a freeway for about 2 miles , crossing the Illinois and Michigan Canal, the Chicago Sanitary and Ship Canal, the Stevenson Expressway (I-55), and the Des Plaines River at a cloverleaf interchange whose ramps had to be built as bridges over these watercourses due to their close proximity to I-55.