Hawaii Revised Statutes Division 1. Government § 273-10

All railroad companies authorized under the laws of the State to operate their railroads by steam power may operate their railroads or any portion of the same by electric power, either by overhead or underground wires or by storage batteries, or by such other methods as may be an improvement upon either; or by compressed air; or by such other motive power as the railroad companies may from time to time elect; provided that a part of the railroad may be operated by one motive power while another or other portions thereof may be operated by another or other motive powers.