Haw. Rev. Stat. § 46-5: Planning and traffic commissions; creation.

The legislative body of any county with a population of less than 100,000 persons shall, without prejudice to the generality of the foregoing powers, and except as otherwise provided, have the following specific powers in addition to any other specific powers provided by law:

(1) County planning commission. To create a county planning commission (A) to formulate a master plan providing for the future growth, development, and beautification of the county in its public and private buildings, streets, roads, grounds, and vacant lots; (B) to formulate subdivision and zoning regulations; and (C) to recommend the establishment of building zones.

(2) County traffic commission. To create a county traffic commission to advise the legislative body in the regulation of traffic.