No vessel owner or operator shall –

1. Signal a drawbridge to open if the vertical clearance is sufficient to allow the vessel, after all lowerable nonstructural vessel appurtenances that are not essential to navigation have been lowered to safety to pass under the drawbridge in the closed position; or
2. Signal a drawbridge to open for any purpose other than to pass through the drawbridge opening.

117.15 Signals

(a) General

1. The operator of each vessel requesting a drawbridge to open shall signal the drawtender and the drawtender shall acknowledge that signal. The signal shall be repeated until acknowledged in some manner by the drawtender before proceeding.
2. The signals used to request the opening of the draw and to acknowledge that request shall be sound signals, visual signals, or radiotelephone communications.
3. Any of the means of signaling described in this subpart sufficient to alert the bridge being signaled may be used.

(b) Sound Signals

1. Sound signals shall be made by whistle, horn, megaphone, hailer, or other device capable of producing the described signals loud enough to be heard by the drawtender.
2. As used in this section, "prolonged blast" means a blast of four to six seconds duration and "short blast" means a blast of approximately one second duration.
3. The sound signal to request the opening of a draw is one prolonged blast followed by one short blast sounded not more than three seconds after the prolonged blast. For vessels required to be passed through a draw during a scheduled closure period, the sound signal to request the opening of the draw during that period is five short blasts sounded in rapid succession.
4. When the draw can be opened immediately, the sound signal to acknowledge a request to open the draw is one prolonged blast followed by one short blast sounded not more than 30 seconds after the requesting signal.
5. When the draw cannot be opened immediately, or is open and shall be closed promptly, the sound signal to acknowledge a request to open the draw is five short blasts sounded in rapid succession not more than 30 seconds after the vessel’s opening signal. The signal shall be repeated until acknowledged in some manner by the requesting vessel.

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.

117.31 Operation of Draw for Emergency Situations

1. When a drawtender is informed by a reliable source that an emergency vehicle is due to cross the draw, the drawtender shall take all reasonable measures to have the draw closed at the time the emergency vehicle arrives at the bridge.
2. When a drawtender receives notice, or a proper signal as provided in 117.15 of this part, the drawtender shall take all reasonable measures to have the draw opened, regardless of the operating schedule of the draw, for passage of the following, provided this opening does not conflict with local emergency management procedures which have been approved by the cognizant Coast Guard Captain of the Port:

1. Federal, State, and Local government vessels used for public safety;
2. Vessels in distress where a delay would endanger life or property;
3. Commercial vessels engaged in rescue or emergency salvage operations; and
4. Vessels seeking shelter from severe weather.