The commissioner of transportation may designate and establish limited access highways as new and additional facilities or may designate and establish any existing road, street or highway within the state as included within a limited access facility. He shall have authority to provide for the elimination of intersections at grade of limited access facilities with any existing road, street or highway, by grade separation or service road or by closing off such road, street, or highway at the right-of-way boundary line of such limited access facility; and after the establishment of any limited access facility, no road, street or highway which is not part of said facility shall intersect the same except at such locations and upon such conditions as the commissioner of transportation shall approve.