33 C.F.R. § 117.21 Signalling for an opened drawbridge.
Title 33 - Navigation and Navigable Waters
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.
Title 33: Navigation and Navigable Waters
PART 117—DRAWBRIDGE OPERATION REGULATIONS
Subpart A—General Requirements
§ 117.21 Signalling for an opened drawbridge.
