[Code of Federal Regulations] [Title 33, Volume 1] [Revised as of July 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 33CFR117.21] [Page 545] TITLE 33--NAVIGATION AND NAVIGABLE WATERS CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PART 117_DRAWBRIDGE OPERATION REGULATIONS--Table of Contents Subpart A_General Requirements Sec. 117.21 Signalling for an opened drawbridge. When a vessel approaches a drawbridge with the draw in the open position, the vessel shall give the opening signal. If no acknowledgment is received within 30 seconds, the vessel may proceed, with caution, through the open draw.