33 CFR 117.19 : Navigation And Navigable Waters (§ 1.01-1 To Parts 404-499) — (§ 1.01-1 To Parts 121-124) — Coast Guard, Department Of Homeland Security (§ 1.01-1 To Parts 121-124) — Bridges (§ 114.01 To § 118.160) — Drawbridge Operation Regulations (§ 117.1 To § 117.1107) — General Requirements (§ 117.1 To § 117.49) — Signalling when two or more vessels are approaching a drawbridge.

When two or more vessels are approaching the same drawbridge at the same time, or nearly the same, time, whether from the same or opposite directions, each vessel shall signal independently for the opening of the draw and the drawtender shall reply in turn to the signal of each vessel. The drawtender need not reply to signals by vessels accumulated at the bridge for passage during a scheduled open period.