Fog Meeting in a Traffic Lane
You are master of the 110-ft passenger vessel Harbor Queen, twin screw, making 9.0 kts on heading 180°T in a traffic lane. Visibility is 0.3 nm in fog; radar is operating. A target is dead ahead at 1.1 nm, bearing 180°T, and over three minutes the bearing remains 180°T while range falls to 0.7 nm. You hear one prolonged blast followed by two short blasts from the target. The vessel is a tug pushing two barges ahead, on a reciprocal course at about 4 kts. The lane is 1,000 ft wide; your starboard side is clear to 0.4 nm. The engine room reports both mains ready for immediate maneuver.
1. Assess the risk of collision and state your sound-signal and speed obligations.
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A constant bearing with decreasing range means risk of collision exists under Rule 7. Closing speed is about 13 kts (9 + 4), so the range is falling roughly 0.22 nm per minute; 0.7 nm is only about 3 minutes away.
You must proceed at a safe speed for the visibility and keep engines ready for immediate maneuver (Rules 6 and 19). As a power-driven vessel making way in fog, you sound one prolonged blast at intervals not exceeding 2 minutes. The target's one prolonged followed by two short blasts identifies a power-driven vessel towing or pushing ahead. Do not wait for the other vessel to solve the problem.
2. What avoiding action do you take, and why not a port turn?
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Alter course substantially to starboard and reduce speed. Rule 19(e) prohibits altering course to port for a vessel forward of the beam unless you are overtaking. A port turn would put you across the tug's bow and reduce CPA.
A starboard alteration, combined with speed reduction, opens the bearing and creates time and sea room. Do not sound maneuvering blasts in fog; those signals are for vessels in sight of one another. Continue radar plotting and listen for the tug's signals. If the bearing still does not open, further reduce speed or stop and back.
3. If radar fails now, what is the judgment call?
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Do not continue at 9 kts. Reduce to bare steerage way, post an extra lookout forward, and sound the proper fog signal. Consider holding at the edge of the lane or anchoring clear of the channel if depth and traffic permit. Use VHF to coordinate if possible, but do not rely on it as a substitute for radar or sound signals. The governing judgment is that without radar in 0.3-nm visibility, 9 kts is not a safe speed.