COLREGs – Principles & Conduct of Vessels

15 January 2026 6 min read Latest Articles

How collision avoidance actually works on a real bridge

Use the links below to jump to any section:

What COLREGs Really Is (and What It Is Not)
Rule 2 – Responsibility: The Rule That Overrides All Others
Rule 5 – Lookout: Human, Electronic, and Organisational
Rule 6 – Safe Speed: Why “Within Limits” Is Not Enough
Rule 7 – Risk of Collision: CPA Lies and Mental Traps
Rule 8 – Action to Avoid Collision: Early, Substantial, and Obvious
Rule 9 – Narrow Channels: Where Theory Breaks Down
Rule 10 – Traffic Separation Schemes: Compliance vs Safety
Stand-On and Give-Way: Why the Names Mislead
When the Other Vessel Is Wrong
COLREGs in Restricted Visibility
The Master, the OOW, and COLREGs Authority
Common COLREGs Failure Patterns
The COLREGs Mindset for Professional Watchkeepers

1. What COLREGs Really Is (and What It Is Not)

COLREGs is not a checklist.
It is not a decision tree.
It is not something you “apply after identifying lights.”

COLREGs is a behavioural framework governing how vessels avoid each other before danger becomes unavoidable.

At sea, compliance with COLREGs is judged after the accident, not during the manoeuvre.

Investigators do not ask:

“Did you know the rule?”

They ask:

“Did your actions reflect good seamanship and early collision avoidance?”

That difference matters.

2. Rule 2 – Responsibility: The Rule That Overrides All Others

Rule 2 is the most powerful and most misunderstood rule in COLREGs.

It states, in effect:

You are responsible for avoiding collision
Even if the other vessel is wrong
Even if the rules appear to give you priority

Rule 2 removes the idea of “having right of way.”

There is no such thing as an absolute right of way at sea.

If you stand on proudly into a collision because “the rules said so,” you have failed Rule 2.

Professional watchkeepers treat Rule 2 as always active.

3. Rule 5 – Lookout: Human, Electronic, and Organisational

A proper lookout is not a person standing near the window.

It is a system.

Rule 5 requires lookout by:

sight
hearing
all available means

“All available means” includes:

radar (properly set and interpreted)
ECDIS awareness
AIS understanding (with its limitations)
bridge team communication

A bridge with excellent equipment and poor teamwork does not have a proper lookout.

A bridge with one overloaded OOW does not have a proper lookout.

4. Rule 6 – Safe Speed: Why “Within Limits” Is Not Enough

Safe speed is situational, not numerical.

It depends on:

visibility
traffic density
manoeuvrability
background lights
weather and sea state
draft and UKC
reliability of sensors

If your speed does not allow you to:

detect a risk
assess it
decide
act
and see the result

then your speed is unsafe — regardless of engine capability or schedule pressure.

Safe speed is about time margin, not knots.

5. Rule 7 – Risk of Collision: CPA Lies and Mental Traps

Risk of collision exists when:

bearing does not appreciably change
CPA is reducing or small
or when doubt exists

Radar CPA is a tool, not truth.

Common failures include:

trusting AIS CPA blindly
misinterpreting ARPA vectors
ignoring visual bearing stability
assuming small CPA is acceptable “because it will pass”

Rule 7 explicitly states:

Assumptions must not be made on the basis of scanty information.

If you are unsure — there is risk.

6. Rule 8 – Action to Avoid Collision: Early, Substantial, and Obvious

This rule defines how to act.

Actions must be:

taken in ample time
be large enough to be obvious
avoid a succession of small changes
result in passing at a safe distance

Tiny course changes to “test the other vessel” are a classic error.

Late manoeuvres force extreme actions.

Professional collision avoidance looks boring on radar — because it happens early.

7. Rule 9 – Narrow Channels: Where Theory Breaks Down

Narrow channels expose the limits of rigid rule-following.

Key realities:

deep-draft vessels have constrained options
bank suction and squat matter
traffic density compresses reaction time
small craft often misunderstand obligations

Rule 9 does not grant dominance — it recognises constraints.

A bridge team must think in terms of who can actually manoeuvre, not who “should.”

8. Rule 10 – Traffic Separation Schemes: Compliance vs Safety

TSS compliance is mandatory — but not absolute.

You must:

proceed in the correct lane
cross at right angles
avoid unnecessary lane changes

But Rule 10 does not excuse collision.

Blindly following a lane while ignoring developing traffic risk violates Rule 2.

TSSs reduce chaos — they do not remove responsibility.

9. Stand-On and Give-Way: Why the Names Mislead

“Stand-on” does not mean “do nothing.”

“Give-way” does not mean “panic manoeuvre.”

Stand-on vessels must:

maintain course and speed initially
monitor the situation
act when collision risk develops

Many collisions happen because the stand-on vessel waited too long, hoping the give-way vessel would comply.

Hope is not a control measure.

10. When the Other Vessel Is Wrong

This is where professionals separate themselves.

If the other vessel:

is not complying
is manoeuvring unpredictably
appears unaware
or is constrained

you must act before the situation becomes critical.

COLREGs does not protect stubbornness.

The goal is no collision, not proving correctness.

11. COLREGs in Restricted Visibility

Restricted visibility changes everything.

Key shifts:

sound signals matter
radar interpretation dominates
visual confirmation may be impossible
assumptions are dangerous

In restricted visibility:

you do not wait for certainty
you reduce speed early
you avoid close-quarters situations entirely

Restricted visibility collisions are almost always speed and delay failures.

12. The Master, the OOW, and COLREGs Authority

COLREGs authority flows like this:

The OOW applies COLREGs continuously
The Master supports and intervenes as required
Responsibility is never delegated away

Calling the Master early is good seamanship, not weakness.

Failure to call is frequently cited in collision reports.

13. Common COLREGs Failure Patterns

Accident investigations repeatedly show:

fixation on one sensor
late decision-making
small ineffective alterations
overconfidence in “stand-on” status
reluctance to challenge
schedule pressure overriding judgement

COLREGs failures are rarely ignorance — they are human factors failures.

14. The COLREGs Mindset for Professional Watchkeepers

Professional application of COLREGs means:

thinking in time margins, not rights
acting early to create space
assuming others may be wrong
prioritising safety over correctness
using the rules to support decisions, not replace them

COLREGs is not about winning an argument at sea.

It is about ensuring everyone goes home.