(a) The purpose of the rules and regulations in this subchapter is to implement certain laws and set forth the requirements for:(1) Locations and clearances of bridges and causeways over the navigable waters;(2) Administration of the alteration of unreasonably obstructive bridges; and(3) Regulation of drawbridge operation.(b) The rules and regulations in this subchapter also describe the procedures, practices, and instructions, which are applicable to the public subject to certain laws governing bridges and causeways over the navigable waters of the United States.USCG-2008-0179, 73 FR 35012 , June 19, 2008, as amended by USCG-2013-0397, 78 FR 39174 , July 1, 2013