A vessel to starboard
Crossing situation. Foundation level, about 3 min. COLREGs Rules 15 & 16.
The situation
You are heading north under power. Another power-driven vessel is approaching from your starboard side. Both vessels are in sight of one another.
Which action best keeps you clear?
- Alter clearly to starboard: Make an early, substantial alteration to pass astern.
- Maintain course and speed: Continue on your present heading.
- Alter to port: Turn toward the crossing vessel’s route.
Lookout: Watch the bearing over time. A steady bearing with decreasing range can indicate risk of collision.
The sound answer
Alter clearly to starboard
You have the other vessel on your starboard side. In this open-water crossing, you must keep out of the way and, if circumstances admit, avoid crossing ahead. A clear starboard alteration is the authored example of passing astern.
Why the other options fall short
Maintain course and speed
You are the give-way vessel in this crossing. Maintaining course and speed leaves the developing risk unresolved. Take early and substantial action to keep well clear.
Alter to port
In this geometry, turning to port takes you toward the other vessel’s route and risks crossing ahead. The give-way vessel should take early, substantial action to keep well clear.
Rules 15 & 16 · Crossing and give-way action
When two power-driven vessels cross so as to involve risk of collision, the vessel with the other on her starboard side keeps out of the way. Give-way action should be early and substantial.