Module 5 - COLREGs
COLREGs Explained for Day Skipper: Rules of the Road
What you will learn
Use the COLREGs as a decision sequence: establish visibility, build the traffic picture, decide whether collision risk exists, identify the applicable encounter rule and monitor the result.
COLREGs are not a list of vessel privileges. They are a shared collision-avoidance system whose starting point is lookout, safe speed and risk assessment—not a quick guess about who is 'right of way'.
The International Regulations for Preventing Collisions at Sea are commonly called COLREGs or IRPCS. Rule 1 applies them to all vessels on the high seas and waters connected with the high seas that are navigable by seagoing vessels. Harbours, rivers and other authorities can make conforming special rules, so charts, notices and harbour directions still need checking.
Part B has three distinct operating contexts. Rules 4–10 apply in any visibility; Rules 11–18 apply when vessels are in sight of one another; Rule 19 applies when vessels are not in sight in or near restricted visibility. That classification comes before deciding that an encounter is overtaking, head-on, crossing or a Rule 18 responsibility case.
Rule 2 prevents a mechanical 'right of way' reading. The owner, master and crew remain responsible for complying with the Rules and for precautions required by ordinary seamanship or special circumstances. A stand-on vessel has an obligation, not a licence to continue into collision, and a vessel that is not to be impeded still has collision-avoidance duties when risk develops.
For revision, use a repeatable loop: maintain the picture, determine risk, identify every applicable rule, take the required early action and observe until the vessels are finally past and clear. AIS labels or a single snapshot can assist orientation but do not decide the rule or replace visual and radar observations.
Look-out
Risk
Action
Responsibilities
Lights & shapes
| Rule / part | Topic | Day Skipper exam focus |
|---|---|---|
| Rules 4–10 | Any visibility | Lookout, safe speed, collision risk, action, channels and TSS |
| Rules 11–18 | Vessels in sight | Sailing, overtaking, head-on, crossing and vessel responsibilities |
| Rule 19 | Not in sight in restricted visibility | Safe speed, engines ready and radar-informed avoiding action |
| Part C | Lights and shapes | Identify vessel type and status by day or night |
| Part D | Sound and light signals | Restricted visibility and manoeuvring signals |
Classify before manoeuvring
At dusk, a yacht sees one vessel visually, detects another only on radar in a fog bank and is approaching a harbour with a local small-craft channel.
1. Build the picture
Maintain sight, hearing and appropriate electronic observations; confirm which contacts are actually in sight.
2. Apply the context
Use Rules 11–18 for the visually observed encounter, Rule 19 for a vessel not in sight in restricted visibility, and check the channel's special directions.
3. Act and monitor
Apply every relevant rule, make any avoiding action early and apparent, and observe the outcome until finally past and clear.
Sense check: If the plan begins with an AIS vessel name or 'power gives way to sail' before visibility and collision risk are established, the sequence has started in the wrong place.
Common mistake or limitation
- There is no absolute right-of-way vessel that can stop maintaining lookout, safe speed or collision-avoidance responsibility.
- Seeing a radar or AIS target is not the same as vessels being 'in sight of one another'; Rule 3 requires visual observation for that term.
Recap
- Rule context comes from visibility, sight and the waterway before vessel hierarchy.
- Rule 2 and Rule 8 keep both responsibility and effective monitoring in the decision.
- Electronic information supplements the picture but does not replace the applicable COLREG rule.
Optional quick check
Section 1 of 9
A contact is detected on radar inside a fog bank but cannot be seen visually. Which encounter framework applies?
Common questions
What does COLREGs stand for?
COLREGs stands for the International Regulations for Preventing Collisions at Sea. They are also known as IRPCS.
Is it COLREG or COLREGs?
The regulations are normally referred to as COLREGs, but people often search for COLREG in the singular. Both refer to the collision regulations at sea.
Which COLREGs rules are most important for Day Skipper?
Day Skipper revision needs working command of lookout, safe speed, collision risk, avoiding action, narrow channels, traffic separation, in-sight encounter rules, Rule 19, lights, shapes and sound signals. The current official text remains authoritative.
Do COLREGs apply to sailing yachts?
Yes. COLREGs apply to all vessels, including sailing yachts. A sailing yacht using its engine is treated as a power-driven vessel.
Keep revising this topic
Sources and factual review
Reviewed 19 August 2026 - Day Skipper Revision.
Build COLREGs confidence
The full COLREGs module breaks the rules into situations, vessel responsibilities, lights, shapes, and practical quiz feedback.