What must the stand-on vessel do?
Keep her course and speed. But once it is apparent the other is not giving way she may manoeuvre, and when collision cannot be avoided by the other's action alone she shall.
Rule 17 (a), (b).
Part of the convention When you can see each other
Keep your course and speed, so your behaviour is predictable. But this is not a duty to hold on into a collision:
- As soon as it becomes apparent that the give-way vessel is not taking appropriate action, you may manoeuvre yourself.
- When you find yourself so close that collision cannot be avoided by her action alone, you shall take the action that best aids to avoid collision.
- In a crossing situation, a power-driven vessel taking action of her own shall not, if the circumstances admit, alter course to port for another power-driven vessel on her own port side.
- This rule does not relieve the give-way vessel of her obligation.
At sea it looks like this
You stand on, she is to starboard and does not turn. At two miles you sound five short blasts. At one mile you reduce speed and turn to starboard yourself: port is barred, that is where she is.
The rule says«…when it becomes apparent to her that the vessel required to keep out of the way is not taking appropriate action in compliance with these Rules, she may take action to avoid collision by her manoeuvre alone.»
Check yourself
Acting alone in a crossing situation, which way must you not turn?
To port, if the other vessel is on your own port side.
Rule 17 (c).