COLREGS Rules 11-15: Vessels in Sight of One Another
Explained for Gen Z Merchant Seafarers
Part 1: Rule 11 – Scope & Application (30 seconds)
The Simple Rule:
Rule 11 establishes that Rules 11-18 apply ONLY when vessels are in sight of one another.
What “In Sight” Means:
“Vessels are deemed to be in sight of one another only when one can be observed visually from the other.”
Translation: You must be able to SEE the other vessel. Not on radar, not on AIS—VISUALLY.
Why This Matters:
Rules 11-15 determine RIGHT-OF-WAY (who must move, who must hold course/speed)
These rules only apply when you can see each other
If you CANNOT see the other vessel visually, these rules don’t apply; Rule 19 (restricted visibility rules) applies instead
Real Scenario:
Your bulk carrier is transiting at night in moderate visibility (2 NM). You detect a vessel on radar 6 NM ahead. Can you see it visually? NO.
Therefore, Rules 11-15 do NOT apply yet. Keep monitoring. When you can see the vessel’s lights visually (typically at 1-2NM), THEN Rules 11-15 apply.
Critical Caveat:
Radar and AIS are TOOLS for lookout but do NOT determine “in sight.” Visual observation is the determining factor.
Part 2: Rule 12 – Sailing Vessels (1.5 minutes)
When Does Rule 12 Apply?
Two conditions MUST exist:
1. BOTH vessels are sailing vessels (no engines propelling them forward)
2. They are approaching so as to involve the risk of collision
❌ NOT Rule 12: One vessel is power-driven; one is sailing
❌ NOT Rule 12: Two sailing vessels detected on radar but not yet in visual sight
✅ Rule 12: Two sailing vessels visible to each other, converging courses, risk of collision exists
The Wind Rule – Three Scenarios:
Scenario 1: Opposite Wind Sides
Rule 12(a)(i):
“When each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other.”
Example: Your sailing yacht has wind on the port side (wind coming from left). You see another sailing yacht approaching with wind on the starboard side (wind coming from the right).
Action: YOUR vessel (port-side wind) must move. The other vessel (starboard-side wind) is the stand-on vessel.
Remember: Port-side wind = give way. Starboard-side wind = stand-on.
Scenario 2: Same Wind Side (Both Port or Both Starboard)
Rule 12(a)(ii):
“When both have the wind on the same side, the vessel which is to windward shall keep out of the way of the vessel which is to leeward.”
Example: Both sailing yachts have wind on the starboard side. One is windward (further upwind); one is leeward (further downwind).
Action: The WINDWARD vessel (higher up) gives way. The LEEWARD vessel (lower down) is a stand-on.
Remember: Upwind = give way. Downwind = stand-on.
Scenario 3: Can’t Determine Wind Direction
Rule 12(a)(iii):
“If a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether the other vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other.”
Example: You have wind on the port side. You see another vessel to your windward, but can’t clearly see which side their sails are on.
Action: YOU give way (vessel with port-side wind always gives way in doubt).
Rule 12(b) – Determining Windward Side:
“The windward side shall be deemed to be the side opposite to that on which the mainsail is carried.”
Translation: Look at where the mainsail is. The windward side is the OPPOSITE side.
Example: You see a yacht with its mainsail on the port side → windward side is STARBOARD.
Critical Point for Merchant Ships:
Most merchant vessels are power-driven, so Rule 12 rarely applies in merchant shipping. However, if a merchant ship’s engine is off and it’s under full sail (unlikely but possible for training ships), Rule 12 applies.
Part 3: Rule 13 – Overtaking (1.5 minutes)
The Golden Rule of Overtaking:
“Any vessel overtaking any other shall keep out of the way of the vessel being overtaken.”
Translation:
The vessel behind is ALWAYS responsible. No exceptions. No VHF agreements. No negotiations.
When Are You Overtaking?
Rule 13(b):
“A vessel shall be deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft her beam.”
The 22.5-Degree Rule Explained:
Imagine the vessel ahead as a clock:
12 o’clock = dead ahead (bow)
3 o’clock = starboard beam (side)
6 o’clock = dead astern (stern)
9 o’clock = port beam (side)
If you approach from anywhere between 3 o’clock and 9 o’clock, PLUS more than 22.5 degrees toward the stern = you are overtaking.
Simplified: If you can see ONLY the stern light at night (NOT the sidelights), you’re overtaking.
Real Merchant Ship Example:
Scenario: Your container ship is overtaking a bulk carrier
Distance: 3 NM behind and to the side
Question: Are you overtaking?
Analysis:
At night, can you see ONLY the bulk carrier’s stern light (white light)?
Can you NOT see the red and green sidelights?
If yes → you are overtaking
Action: You (container ship) are the give-way vessel. You must keep clear.
Rule 13(c) – Doubt Creates Obligation:
“When a vessel is in any doubt as to whether she is overtaking another, she shall assume that this is the case and act accordingly.”
Translation: If you’re UNSURE whether you’re overtaking, ASSUME YOU ARE and stay clear.
Rule 13(d) – Tricky Part: No Bearing Change Exception
“Any subsequent alteration of the bearing between the two vessels shall not make the overtaking vessel a crossing vessel within the meaning of these Rules or relieve her of the duty of keeping clear until she is finally past and clear.”
This Means:
You cannot claim “we’re now a crossing situation” to escape your responsibility as the overtaking vessel.
WRONG Scenario: You’re overtaking. Your bearing to the other vessel starts changing. You think: “Now we’re crossing; the crossing rules apply instead. I can alter to starboard.”
CORRECT: You remain the overtaking vessel and must STAY CLEAR. The crossing rules do NOT apply. Overtaking status remains until you’re “finally past and clear.”
How to Know When You’re “Finally Past and Clear”:
The bearing is steady or moving away
The range is increasing continuously
The other vessel is now behind you (astern)
You could now turn toward that vessel without risk (minimum 1-2 NM separation)
Real Collision Case – The Overtaking Violation:
Case: Two cargo vessels, North Sea (2018)
Vessel A (container ship) was overtaking Vessel B (bulk carrier) in a busy shipping lane. When Vessel A was approximately 300meters abeam (parallel), Vessel A’s master altered course to starboard toward the traffic lane, claiming “now we’re in a crossing situation.”
What happened: Vessel B continued on its course. Vessel A turned into Vessel B.
A collision resulted.
Why this was wrong: Rule 13(d) prohibits this. Vessel A was still the overtaking vessel and had NOT reached “finally past and clear” status. Overtaking obligations remained.
Common Student Mistakes ⚠
❌ WRONG: “The vessel ahead agrees to overtaking; now we’re equal.”
✅ RIGHT: Rule 13 applies regardless of agreement. Overtaking vessel stays responsible.
❌ WRONG: “We’re now abeam; the crossing rules now apply.”
✅ RIGHT: You remain overtaking vessel until finally past and clear. Crossing rules do NOT replace overtaking obligations.
❌ WRONG: “We’re very close; the nearest approach is 50m; we’re clearly different situations.”
✅ RIGHT: Distance doesn’t matter. If bearings are altered but you haven’t completed the overtaking manoeuvre with final clearance, you’re still overtaking.
Part 4: Rule 14 – Head-On Situation (1.5 minutes)
The Definition:
“When two power-driven vessels are meeting on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter her course to starboard so that each shall pass on the port side of the other.”
Translation:
Vessels approaching head-on = both alter to starboard (right) to pass left-side-to-left-side (port-to-port).
How to Recognise Head-On:
Rule 14(b):
At night: You see the other vessel’s masthead lights in a line (or nearly in a line) AND/OR both red and green sidelights together
By day: You observe the other vessel’s forward aspect (the front/bridge view)
Real Example – Container Ships:
Scenario: Your container ship sees another container ship approaching at night.
Visual observation:
You see ONE white masthead light
You see BOTH red (port) and green (starboard) sidelights in the same view
You do NOT see the stern light (white light at the back)
Conclusion: HEAD-ON situation. Both vessels must alter to starboard.
The 22-Degree Rule:
“Reciprocal or nearly reciprocal courses” typically means within approximately 22 degrees either side of a direct head-on approach.
Example: Your course 010°, other vessel’s course 190° = directly reciprocal (180° difference) = head-on.
Other vessel’s course 200° = nearly reciprocal (about 190° difference) = still head-on.
Critical: Rule 14(c) – Doubt Creates Obligation:
“When a vessel is in any doubt as to whether such a situation exists, she shall assume that it does exist and act accordingly.”
Example Scenario:
You see both sidelights + uncertain about the masthead light alignment
Radar CPA shows 0.3 NM (close)
But you’re uncertain if it’s truly head-on
Action: ASSUME it’s head-on and alter to starboard.
Common Mistake – ARPA vs. Rule:
❌ WRONG: “ARPA shows CPA 1.2 NM; not a true head-on; we’ll maintain course.”
✅ RIGHT: If visual indicators suggest head-on (both sidelights + masthead lights aligned), it IS head-on. ARPA is a tool, notthe rule. Alter to starboard.
Stand-On Vessel Responsibility:
Rule 14 creates NO “stand-on” vessel. BOTH vessels are equally responsible for altering.
This is different from Rules 15, 16, 17 (crossing, give-way, stand-on).
Part 5: Rule 15 – Crossing Situation (1.5 minutes)
The Definition:
“When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel.”
Translation:
One vessel sees the other’s red sidelight = give way vessel. The other vessel sees your red sidelight = stand-on vessel.
Simple Memory Aid:
Red light means STOP (give way); Green light means GO (hold course/speed)
If you see RED (other vessel’s port side) = YOU are on THEIR port side = YOU have an obligation to move.
How to Recognise Crossing:
You see the approaching vessel’s red sidelight (port light):
Red sidelight visible = other vessel is to your port side
Therefore, the other vessel has YOU on its starboard side
Therefore, YOU are the give-way vessel
Simple rhyme: “If to starboard a red does appear, ’tis your duty to keep clear”
Real Merchant Ship Example:
Scenario: Two container ships in open water
Your vessel: Course 090° (heading east), speed 18 knots
Other vessel: Course 180° (heading south), speed 16 knots
Visual observation: You see the OTHER vessel’s RED sidelight
Analysis:
Red light = other vessel is to YOUR port (left)
The other vessel has YOU on its starboard (right)
You are the GIVE-WAY vessel
The other vessel is the STAND-ON vessel (maintains course/speed)
Action:
Alter course to starboard and/or reduce speed
Do NOT cross ahead of the stand-on vessel
Maintain your action until the other vessel is safely clear
Rule 15 – The Avoid-Crossing-Ahead Clause:
“If the circumstances of the case admit, avoid crossing ahead of the other vessel.”
Translation: If possible, pass ASTERN (behind) the stand-on vessel, NOT across its bow.
Why? Because crossing ahead is more dangerous and requires greater precision.
Two Methods of Giving Way in Crossing:
Method 1: Alter Course to Starboard (Preferred)
Altering to starboard (right) shows clear action
Most visible to other vessel
Creates an obvious course change
Preferred in open water with sufficient sea room
Method 2: Reduce Speed or Stop
Useful in confined waters
Reduces approach speed
Allows time for a stand-on vessel to pass ahead
Preferred when sea room is limited
Restrictions on Altering to Port:
Rule 15(c):
“A power-driven vessel which takes action in a crossing situation in accordance with subparagraph (a) (2) of this Rule to avoid collision with another power-driven vessel shall, if the circumstances of the case admit, not alter course to port for a vessel on her own port side.”
Translation: If the other vessel is on YOUR port (left) side, DO NOT alter to port (left).
Why? Because altering to port might bring you CLOSER to the other vessel’s track.
Example:
Other vessel approaching from your port side (you see green light)
You want to give way
DO NOT alter left (to port) = you’d move toward them
DO alter right (to starboard) = you’d move away
Common Student Mistakes ⚠
❌ WRONG: “We see green light; we have right-of-way; we maintain course.”
✅ RIGHT: Green light = other vessel is to your starboard (right) side = they have YOU on THEIR port = you’re the give-way vessel.
❌ WRONG: “As the give-way vessel, we can maintain course and speed.”
✅ RIGHT: Rule 15 requires the give-way vessel to take early and substantial action.
❌ WRONG: “We can cross ahead if we do it quickly.”
✅ RIGHT: Rule 15 says avoid crossing ahead “if circumstances admit.” Don’t assume you can.
Part 6: Integration – Rules 11-15 in Practice (1 minute)
The Decision Tree:
Step 1: Can you see the other vessel visually?
NO → Rule 19 (restricted visibility) applies; NOT Rules 11-15
YES → Continue to Step 2
Step 2: What type of vessels are you?
Two sailing vessels → Rule 12 (wind rules)
One sailing, one power-driven → Rule 18 (responsibilities)
Two power-driven → Continue to Step 3
Step 3: What is your relative position?
One behind the other (bearing >22.5° abaft beam) → Rule 13 (overtaking)
Head-on (masthead lights aligned + both sidelights) → Rule 14 (head-on)
Crossing (one sees other’s sidelight) → Rule 15 (crossing)
Step 4: Act accordingly per the rule
Real Scenario – Integration Example:
Situation: Your bulk carrier (night time, good visibility) observes another vessel.
Observation 1: “We see both red and green sidelights + masthead lights nearly aligned”
Analysis: HEAD-ON situation (Rule 14)
Action: Alter to starboard; both vessels bear equal responsibility
Observation 2: “We see only RED sidelight (port light); vessel is off our port bow”
Analysis: CROSSING situation (Rule 15), and we are the GIVE-WAY vessel
Action: Alter to starboard and/or reduce speed; avoid crossing ahead
Observation 3: “We see only the other vessel’s STERN light (white light); we are approaching from 25° abaft beam”
Analysis: OVERTAKING situation (Rule 13); we are the overtaking vessel
Action: We are the give-way vessel; maintain course/speed by the stand-on vessel; we stay clear until finally past and clear
Part 7: Common Exam Mistakes & Misunderstandings
Rule 11 Mistakes:
❌ WRONG: “ARPA shows the vessel; therefore Rule 11-15 apply.”
✅ RIGHT: Rule 11 requires VISUAL observation. Radar alone doesn’t establish “in sight.”
Rule 12 Mistakes:
❌ WRONG: “A bulk carrier with engine off under full sail with wind on port = stand-on vessel.” ✅ RIGHT: Wind onport = give-way vessel; must keep out of the way of starboard-wind vessel.
❌ WRONG: “Port-side wind always means you stand on.”
✅ RIGHT: Port-side wind = give-way; port-side wind always moves.
Rule 13 Mistakes:
❌ WRONG: “After the vessel ahead agreed by VHF, our overtaking responsibility ends.”
✅ RIGHT: Rule 13 applies regardless of VHF agreement. We’re responsible until finally past and clear.
❌ WRONG: “We altered our bearing by 30 degrees; now we’re crossing, not overtaking.”
✅ RIGHT: Bearing change doesn’t change overtaking status. Rule 13(d) prohibits this escape.
❌ WRONG: “At 1 km separation, we can claim we’re finally past and clear.”
✅ RIGHT: “Finally past and clear” requires safe separation (typically 2+ NM), no collision risk.
Rule 14 Mistakes:
❌ WRONG: “ARPA shows CPA 2 NM; not head-on; we maintain course.”
✅ RIGHT: If both sidelights + masthead lights aligned = head-on. ARPA is supplementary; visual is determinative.
❌ WRONG: “We’re head-on; one vessel maintains course; the other alters.”
✅ RIGHT: Both vessels ALTER to starboard. There’s no stand-on vessel in head-on.
❌ WRONG: “We’re uncertain about head-on; we’ll wait and see.”
✅ RIGHT: Rule 14(c): “If in doubt, assume head-on and act accordingly.”
Rule 15 Mistakes:
❌ WRONG: “Green light visible = we have right-of-way.”
✅ RIGHT: Green light = other vessel on YOUR starboard = THEY have right-of-way; YOU give way.
❌ WRONG: “We can cross ahead of the stand-on vessel in a crossing.” ✅ RIGHT: Rule 15 says avoid crossing ahead if circumstances admit.
❌ WRONG: “The give-way vessel can alter to port if needed.”
✅ RIGHT: Rule 15(c) prohibits altering to port for a vessel on your port side.
Part 8: Quick Reference – The 5-Minute Takeaway
Rule 11 (Scope): Rules 11-15 apply ONLY when vessels are in sight of one another visually (not just radar/AIS).
Rule 12 (Sailing): Two sailing vessels approaching: wind-on-port vessel gives way; same-wind vessels: windward vessel gives way.
Rule 13 (Overtaking): Overtaking vessel (>22.5° abaft beam) is ALWAYS give-way. Stays responsible until finally past and clear. Bearing changes don’t alter this. VHF agreements don’t override this rule.
Rule 14 (Head-On): Two power-driven vessels meeting reciprocally (both see masthead lights aligned + both sidelights): BOTH alter to starboard. No stand-on vessel. Both bear equal responsibility.
Rule 15 (Crossing): Red sidelight visible = other vessel on YOUR port side = YOU give way. Pass astern if possible; never cross ahead if avoidable.
Bridge Team Responsibilities – Rules 11-15
For the Master:
✓ Brief the bridge team on Rule 11-15 requirements before arrival/departure ✓ Be available on the bridge during complex encounters
✓ Ensure OOW is trained on right-of-way determination
For the OOW:
✓ Maintain continuous visual observation (not just radar)
✓ Determine type of situation (overtaking, head-on, crossing) ✓ Identify give-way vs. stand-on responsibilities
✓Take early and substantial action as the give-way vessel ✓ Maintain action until the other vessel safely clears
For the Helmsman and Lookout:
✓ Execute course alterations smoothly and promptly
✓Alert OOW to approaching traffic
✓Acknowledge all helm orders
✓ Call out bearing changes on targets
Bridge Scenario – Integration of Rules 11-15
Situation: Your container ship (18 knots, course 090°) is transiting open water. Visibility is good. You observe two vessels approaching.
Vessel A (Tanker):
Visual observation: RED sidelight + white stern light + green sidelight (all visible together)
Bearing: 30° off starboard bow
Closest point of approach: estimated 1.0 NM
Vessel B (Bulk Carrier):
Visual observation: RED sidelight only; NO sidelights or masthead lights of Vessel B visible
Bearing: 45° abaft port beam
Position: approaching from 50° abaft beam
Analysis:
Vessel A:
Both sidelights visible = NOT head-on or crossing as typically defined
Assessment: Likely a crossing situation with RED light visible
Bearing 30° off starboard = Vessel A on YOUR port side
YOU have Vessel A on your PORT side; Vessel A has YOU on THEIR starboard
Therefore: Vessel A is a GIVE-WAY vessel; you are a STAND-ON
Action: MAINTAIN course and speed; monitor for Vessel A’s action
Vessel B:
RED sidelight only; no other lights
Bearing 45° abaft beam = OVERTAKING situation (>22.5° abaft beam)
You are the OVERTAKING vessel
Action: Maintain Vessel B’s course/speed; YOU must stay clear; do NOT alter course to cross ahead
Bridge Procedures:
1. Sound fog signals as appropriate
2. Ensure the engine is on standby
3. Helmet manned; all lookout stations alert
4. Radar and AIS monitoring are continuous
5. Alert Vessel A that you’re monitoring (AIS, VHF if appropriate)
6. Document all bearing changes and relative positions
You must be logged in to post a comment.