Haw. Rev. Stat. § 264-62

The director of transportation, acting alone or in cooperation with any federal, or local agency, may plan, designate, establish, regulate, vacate, alter, realign, widen, improve, maintain, and provide controlled-access facilities for public use whenever the director is of the opinion that traffic conditions, present or future, will justify the special facilities. The director may regulate, restrict, or prohibit the use of the controlled-access facilities by the various classes of vehicles or traffic by means of signs and other devices to promote the safe and efficient use of the facilities.