Rules 9-10

COLREGS Rules 9-10: Confined Spaces Navigation

Explained for Gen Z Merchant Seafarers

Part 1: Rule 9 – Narrow Channels (2.5 minutes)

What is a Narrow Channel or Fairway?

Narrow Channel: A natural or dredged lane restricted on either side by shallow water, often marked by buoys.

Fairway: A dredged lane in open water (or somewhat open water) maintained by a port authority, used to route vessels away from hazards, oil platforms, or shallow water.

Key Point: “Narrow” is NOT a specific width. It depends on the vessel type and circumstances. A fairway that’s safe for a small fishing boat might be too narrow for a deep-loaded bulk carrier.

Real Examples:

Thames Estuary (London): Narrow channel with restricted depth and width

Singapore Strait: Complex narrow waters with multiple fairways

Malacca Strait: Deep-water fairways for loaded tankers

Suez Canal: Extremely narrow channel (only about 192 meters wide in some sections!)

Panama Canal: Narrow locks and approach channels

Part 2: Rule 9(a) – Keep to Starboard Side

The Rule:

“A vessel proceeding along the course of a narrow channel or fairway shall keep as near to the outer limit of the channel or fairway which lies on her starboard side as is safe and practicable.”

In Plain English:

Stay on the right side of the channel. (Follow US road traffic pattern)

If the channel runs north-south, keep to the starboard (right) side. This ensures head-on traffic meets on opposite sides—like two-way traffic on a highway.

The Logic:

Imagine two vessels approaching each other in a narrow channel:

Vessel A stays on the starboard side (right)

Vessel B stays on the starboard side (right)

They meet right-side-to-right-side (port-to-port passing) ✓ SAFE

If vessels don’t follow this rule:

Vessel A stays on the center or port side

Vessel B stays on center or port side

They approach head-on ✗ COLLISION RISK

Important Qualifier: “As Safe and Practicable”

You CAN move from the starboard side IF necessary:

❌ DON’T: “Rule 9(a) says stay on starboard side, so we must, even if it means running aground on shallow water.”

✅ DO: “If staying on the starboard side is unsafe due to shallow water or an obstruction, you can move toward center or port side, but only as much as necessary.”

Real Merchant Ship Example – The Capesize Collision:

Case: Capesize Bulk Carrier in Port Fairway (2019)

A 325-meter capesize bulk carrier (Vessel A) was inbound to port, fully loaded with a 17.8-meter draft. The fairway depth was 18+ meters, but the surrounding water was only 17 meters. The vessel was constrained by draft and forced to stay in the center of the narrow fairway.

An outbound Panamax carrier (Vessel B, 225m) was departing. Both pilots agreed verbally to pass “starboard to starboard”(green to green).

The mistake: Vessel B suddenly altered to starboard at 0.5 NM range, trying to cross ahead of Vessel A and pass “port to port” instead.

What happened: Vessel B violated Rule 9(a) and 9(d) by:

Not staying on the starboard side of the outbound lane
Attempting to cross the fairway (impeding Vessel A’s passage)

Result: COLLISION. Vessel B’s port side hull was torn open.

Lesson: Even verbal agreements (VHF “green to green”) are SECONDARY to COLREGS. Vessel B violated Rule 9—vessels constrained by draft have priority to use the fairway.

Part 3: Rule 9(b) & (c) – Special Restrictions for Small Vessels

Rule 9(b) – Small Vessels & Sailing Vessels:

“A vessel of less than 20 meters in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway.”

Translation:

Small vessels and sailboats MUST NOT block large ships that are confined to the channel.

Who is a “small vessel”? Less than 20 meters (about 65 feet)

Examples of affected vessels:

Small fishing boats

Sailboats

Yachts under 20m

Small tugboats

If you are in a small vessel and see a large ship approaching in a narrow channel:

Move to the side (if possible)

Exit the channel if possible

Reduce speed and give way

Do NOT stay in the middle of the channel

Rule 9(c) – Fishing Vessels:

“A vessel engaged in fishing shall not impede the passage of any other vessel navigating within a narrow channel or fairway.”

Translation:

Fishing vessels actively fishing (nets deployed, restricting manoeuvrability) CANNOT block the channel.

Tricky Point: This applies to fishing vessels ACTIVELY FISHING, not all fishing vessels.

❌ WRONG: “A fishing boat’s presence in a narrow channel always blocks large ships.”

✅ RIGHT: A fishing boat engaged in fishing (nets restricting movement) must move. A fishing boat just transiting through can stay, but should not impede large ships.

Real Example:

Scenario: Your bulk carrier in a narrow channel encounters a fishing vessel

Situation A (Fishing actively):

The fishing vessel has nets deployed

You’re approaching

The fishing vessel is “engaged in fishing”

They MUST move or alter course to let you pass

If they don’t, Rule 9(c) violation

Situation B (Just transiting):

The fishing vessel is in the channel, but NOT fishing

You’re approaching

The fishing vessel CAN stay if there’s sea room

But they should not impede your passage

If they’re taking up the whole channel, they must move

Part 4: Rule 9(d) – Don’t Cross If It Impedes

The Rule:

“A vessel shall not cross a narrow channel or fairway if such crossing impedes the passage of a vessel which can safely navigate only within such channel or fairway.”

Translation:

Do NOT cross a narrow channel in front of a large ship that’s confined to that channel.

The Logic:

In a narrow channel, large deep-drafted ships have NO ALTERNATIVES:

Can’t go around (water too shallow on sides)

Can’t stop quickly (deep-loaded tanker takes 10+ minutes to stop)

Can’t deviate (constrained by draft)

If you cross in front of them, they have NO OPTIONS to avoid a collision.

When Crossing is FORBIDDEN:

A vessel (any size) approaches the channel to cross it. Approaching down the channel is a large constrained-by-draft vessel.

❌ FORBIDDEN: You cross if the deep-drafted vessel cannot avoid yo

✅ ALLOWED: You cross ONLY if you’re 100% certain the large vessel can pass safely without taking avoiding action

Sound Signal – Rule 34(d):

If the constrained vessel is uncertain about your intentions, they can sound:

At least 5 short rapid blasts = “I am uncertain of your intentions; take action!”

Example dialogue:

You (small vessel) start to cross the channel

Large constrained vessel sounds 5 blasts

Translation: “Stop! You’re impeding me!”

You must STOP or go back

Real Example – Merchant Ships:

Scenario: Container ship approaching a narrow channel approach

You’re on a small general cargo ship. A massive container ship (40,000 TEU, deep-loaded) is approaching down a narrow channel approach. You’re on the opposite side and consider crossing the channel to get to your destination port.

Analysis:

Container ship: Constrained by draft, cannot deviate

You: Small vessel, can navigate anywhere

The choice is YOURS whether to cross

Correct action: DO NOT CROSS. Let the container ship pass first. This is not a suggestion; it’s Rule 9(d).

Why? Because you have the flexibility, they don’t.

Part 5: Rule 9(e) – Overtaking in Narrow Channels (1 minute)

The Challenge:

In a narrow channel, there’s limited sea room for a vessel behind to pass a vessel ahead. Overtaking needs special procedures.

Rule 9(e)(i) – Sound Signal Protocol:

If overtaking is possible ONLY if the vessel ahead takes action to permit it:

Step 1: The Overtaking Vessel (Ship Behind) Signals Intent

Sound one of these signals:

2 prolonged blasts + 1 short blast = “I intend to overtake you on your starboard side”

2 prolonged blasts + 2 short blasts = “I intend to overtake you on your port side”

Step 2: The Vessel Ahead Responds

The ship ahead answers with:

1 prolonged + 1 short + 1 prolonged + 1 short blast = “Yes, you may overtake me; I am taking action to permit it”

At least 5 short rapid blasts = “I do NOT agree; you cannot overtake” (if in doubt or refusing)

Step 3: Overtaking Vessel Verifies Action

Confirm the vessel ahead has moved to the side

Only then proceed with overtaking

If the ahead vessel sounds 5 blasts even after agreeing, ABORT overtaking

Step 4: Monitor Throughout

Continue monitoring until fully clear

If the ahead vessel makes any unexpected move, sound 5 blasts immediately

Don’t assume safe passage; stay alert

Critical Rule 9(e)(ii) – Responsibility Remains:

“This rule does not relieve the overtaking vessel of her obligation under Rule 13.”

Translation: Even if the vessel ahead agrees and moves, you (the overtaking vessel) are still RESPONSIBLE.

❌ WRONG: “The vessel ahead agreed; now if we collide, it’s their fault.”

✅ RIGHT: Agreeing to overtaking doesn’t absolve your responsibility. You must verify adequate sea room and abort if unsafe.

Example:

Vessel A (ahead) signals agreement. Vessel B (behind) starts overtaking. Midway, Vessel A’s engine fails and they drift back intoVessel B’s path. Collision results.

Who is responsible? Vessel B. Even though Vessel A failed to maintain their side of the channel, Vessel B was the overtaking vessel and had the responsibility to monitor and abort if conditions changed.

Part 6: Rule 9(f) – Blind Bends & Obstructions (30 seconds)

The Rule:

“A vessel nearing a bend or an area of a narrow channel or fairway where other vessels may be obscured by an intervening obstruction shall navigate with particular alertness and caution and shall sound the appropriate signal prescribed in Rule 34(e).”

Translation:

When approaching a bend or obstruction where you can’t see ahead, sound a warning signal.

The Signal:

Sound: 1 prolonged blast (about 4-6 seconds on the ship’s horn)

This is the same as the fog signal for a power-driven vessel—it warns traffic around the bend.

Why It Matters:

Imagine a narrow river channel with a sharp bend ahead. You can’t see past the bend, but another vessel might be coming around it. By sounding a prolonged blast:

You warn them you’re approaching

They warn you if they’re coming

Collision avoidance is possible

Real Scenario:

Your bulk carrier is transiting a narrow, dredged fairway with several sharp bends (common in river approaches to ports). As you approach each bend, you sound a prolonged blast. This alerts vessels on the other side that you’re coming.

Part 7: Rule 10 – Traffic Separation Schemes (2.5 minutes)

What is a Traffic Separation Scheme (TSS)?

A TSS is a maritime traffic management system designed to organise the flow of shipping in busy, congested waters.

Think of it like highway lanes: all traffic moving in one direction uses one lane; opposite traffic uses another lane; a separation zone (median) keeps them apart.

Components of a TSS:

Traffic Lanes – Routes for vessels sailing in one direction

Marked on charts in purple

Each lane has a “general direction of traffic flow”

All vessels in that lane sail the SAME direction

Separation Zone/Lines – Buffer between opposite-direction lanes

Marked by dotted lines or areas on charts

MUST NOT be entered except in emergencies or for fishing

Inshore Traffic Zone – Shallow water zone closer to shore

For small vessels (<20m), sailing vessels, and fishing vessels only

Large ships should NOT use inshore zones

Termination Areas – Where TSSs begin and end

MOST DANGEROUS (highest traffic density and crossing situations)

Requires heightened alertness

Real TSS Examples:

Dover Strait/English Channel: One of the world’s busiest, separating UK-France traffic

Singapore Strait: Extremely complex, with multiple lanes and inshore zones

Malacca Strait: Major deep-water routing for large tankers

Gulf of Suez: TSS for Suez Canal approaches

New York Approaches: Separation for incoming and outgoing traffic

Part 8: Rule 10 – Proceeding in Traffic Lanes

Rule 10(b)(i) – General Direction of Traffic Flow:

“A vessel using a traffic separation scheme shall proceed in the appropriate traffic lane in the general direction of traffic flow for that lane.”

Translation:

Follow the lane in the same direction as all the other vessels in that lane.

What This Means:

❌ WRONG: You’re in the eastbound lane but sailing west to save time.

✅ RIGHT: You’re in the eastbound lane and sailing east with all other traffic.

The logic: Head-on collisions happen when vessels sail against traffic flow. TSS prevents this by forcing all vessels in the onelane to sail in the same direction.

Rule 10(b)(ii) – Keep Clear of Separation Lines:

“So far as practicable, keep clear of a traffic separation line or separation zone.”

Translation:

Don’t navigate on the boundary line between lanes or in the separation zone. Stay well within your lane.

What This Means:

❌ WRONG: Laying a course exactly on the centerline of the lane while traffic flows both sides ✅ RIGHT: Laying a course offset from the centerline, staying clearly within one lane

Why? Because:

The separation line is the edge (danger zone)
If traffic in the opposite lane drifts slightly, you meet head-on
If you drift, you hit the opposite traffic
Staying in the center (but away from the exact centerline) is safer

Part 9: Rule 10 – Joining & Leaving Traffic Lanes

Rule 10(b)(iii) – Normal Entry & Exit:

“Normally join or leave a traffic lane at the termination of the lane, but when joining or leaving from either side shall do so at as small an angle to the general direction of traffic flow as practicable.”

Translation – Two Methods:

Method 1: Normal Entry/Exit (PREFERRED)

Join/leave at the END of the lane (termination point)

This is the safest method

No crossing situations required

Method 2: Side Entry/Exit (ONLY IF NECESSARY)

You must join/leave from the side (not at termination)

Execute at as small an angle as practicable to traffic flow (minimum ~30 degrees, ideally 15-20 degrees)

NOT at 90 degrees (that’s for crossing, different rule)

Example Angles:

Correct side entry: 20-degree angle to traffic flow (nearly parallel)

WRONG side entry: 90-degree angle (creates crossing situation)

Why small angle? Because:

You spend less time in the lane
Traffic can see you easily
Less chance of collision

Rule 10(c) – Crossing Traffic Lanes:

“A vessel shall, so far as practicable, avoid crossing traffic lanes, but if obliged to do so shall cross on a heading as nearly as practicable at right angles to the general direction of traffic flow.”

Translation:

Avoid crossing. If you must cross, do it at 90 degrees (perpendicular). (Ship’s heading)

Why 90 Degrees?

Shortest crossing time – minimises exposure to traffic

Most obvious to other vessels – visible on radar and visually

Time to react – other vessels have maximum time to see you and react

Real Example – What NOT to Do:

Scenario: Your container ship needs to cross a TSS to reach a port

❌ WRONG: You cross at 60 degrees (diagonal), trying to shortcut your route

Why wrong:

Takes longer to cross

You’re in the lane longer

Other traffic can’t easily predict your path

Higher collision risk

✅ RIGHT: You alter course to cross at 90 degrees, then alter back

Why right:

Shortest crossing time

Obvious to all traffic

Reduces collision risk

Part 10: Rule 10 – Separation Zones & Emergencies

Rule 10(e) – When Can You Use Separation Zones?

“A vessel other than a crossing vessel or a vessel joining or leaving a lane shall not normally enter a separation zone or cross a separation line except:”

Three Exceptions:

Exception 1: Emergency to Avoid Immediate Danger

Engine failure approaching another vessel

Fire on bridge

Severe weather requiring shelter

NOT for saving time or fuel

Exception 2: Fishing

A fishing vessel may fish in the separation zone

But it must not impede traffic in the lanes

Exception 3: Navigation Safety Operations

Cable-laying vessels

Wreck-removal operations

Dredging for safety

Real Example:

Your container ship is transiting the Dover Strait TSS when the engine fails. You’re in a separation zone and cannot restart. This is an EMERGENCY. You can:

Announce to VTS “We have engine failure, drifting in the separation zone”

Display appropriate signals (two red balls for not under command)

Request assistance

This is acceptable under Rule 10(e)(i).

Part 11: Rule 10 – Termination Areas (CRITICAL)

Rule 10(f) – Particular Caution Near Terminations:

“A vessel navigating in areas near the terminations of traffic separation schemes shall do so with particular caution.”

Why Termination Areas Are Most Dangerous:

At a TSS termination, you have:

Opposing traffic converging

Vessels joining/leaving from all directions

Highest traffic density

Maximum crossing situations

Minimal sea room for avoiding action

Bridge Procedures for Termination Areas:

✓Post additional lookout on bridge wings ✓Have 2 radars operating with ARPA on both

✓Main engine on standby (ready to increase/decrease speed) ✓Helmsman alert(ready for immediate course changes)

✓All navigation equipment tested (AIS, radar, compass, GPS) ✓Master or Chief Officer onbridge (senior officer present in critical area) ✓Reduce speed compared to normal lane transit speed

Real Example – The General Cargo Incident:

Two vessels were navigating near a TSS termination. Both were making course changes. An officer on Vessel A did not realizeVessel B was already executing a 360-degree turn. When Vessel A suddenly altered starboard, it turned into the path of Vessel B’s turn.

Result: COLLISION

Why? The termination area requires heightened awareness and continuous monitoring—which was NOT maintained.

Part 12: Rule 10 – Vessels NOT Using TSS

Rule 10(h) – Stay Away from Traffic Separation Schemes:

“A vessel not using a traffic separation scheme shall avoid it by as wide a margin as is practicable.”

Translation:

If you’re not using the TSS, don’t go near it. Avoid by a WIDE margin.

Example Violations:

❌ WRONG: Your small fishing vessel stays just outside the TSS boundary, close enough to interfere with traffic

✅ RIGHT: Your fishing vessel stays several miles away from the TSS, well clear of all traffic

Why This Matters:

If you’re fishing close to a TSS boundary:

A vessel in the lane might deviate to avoid you

This creates collision risk with other lane traffic

You could be held liable for disrupting traffic flow

Part 13: Common Student Mistakes & Misunderstandings

RULE 9 MISTAKES:

Mistake 1: Starboard Side Absolute

❌ WRONG: “Rule 9(a) says stay on starboard side NO MATTER WHAT.”

✅ RIGHT: Stay on starboard side “as safe and practicable.” If shallow water makes it unsafe, move to center/port temporarily.

Mistake 2: Small Vessels Can Always Enter

❌ WRONG: “A 19-meter vessel can fish anywhere in a narrow channel.”

✅ RIGHT: Rule 9(b) says if you’re under 20m, you CANNOT impede a large constrained vessel. You must move if blocking.

Mistake 3: Fishing Permit

❌ WRONG: “Any fishing vessel can fish anywhere in a narrow channel.”

✅ RIGHT: Rule 9(c) applies to vessels “engaged in fishing” (actively fishing with restricting gear). Just anchored fishermen don’t count.

Mistake 4: Crossing is Always Allowed

❌ WRONG: “We can cross a narrow channel if we see no traffic approaching.”

✅ RIGHT: Rule 9(d) forbids crossing if it impedes any vessel that can only navigate within the channel. Even a distantvessel counts if constrained.

Mistake 5: Sound Signal Agreement Means Permission

❌ WRONG: “The vessel ahead agreed to overtaking by sounding the acceptance signal, so we don’t need to monitor—it’s their responsibility.”

✅ RIGHT: Rule 9(e)(ii) says you (overtaking vessel) retain full responsibility. Monitor continuously; abort if conditions change.

RULE 10 MISTAKES:

Mistake 6: TSS Gives Right-of-Way

❌ WRONG: “We’re in a TSS lane, so we have right-of-way over all other traffic.”

✅ RIGHT: Rule 10(a) says “This rule does not relieve any vessel of her obligation under any other rule.” COLREGS Rules 12-18 still apply.

Mistake 7: Centerline Navigation Safe

❌ WRONG: “Sailing down the exact centerline of a TSS lane is the safest.”

✅ RIGHT: Rule 10(b)(ii) says keep CLEAR of separation lines. Stay offset from centerline; stay within your lane.

Mistake 8: Small Angles When Crossing

❌ WRONG: “When crossing a TSS, we’ll cross at 45 degrees to save time.”

✅ RIGHT: Rule 10(c) requires crossing “as nearly as practicable at right angles” (90 degrees). 45 degrees is wrong.

Mistake 9: Heading vs. Course

❌ WRONG: “We’ll cross the TSS at 90 degrees course to good; wind will blow us off heading but that doesn’t matter.”

✅ RIGHT: Rule 10(c) specifies “heading” not “course.” Your actual heading through the water must be 90 degrees, regardless of wind/tide.

Mistake 10: Separation Zone Emergency

❌ WRONG: “We want to save fuel, so we’ll cut through the separation zone.”

✅ RIGHT: Rule 10(e) allows separation zone only for “immediate danger” (emergency), not convenience or fuel-saving.

Mistake 11: Inshore Zone for Large Ships

❌ WRONG: “The inshore zone looks empty; we’ll use it as a shortcut.”

✅ RIGHT: Rule 10(d) reserves inshore zones for <20m vessels, sailing vessels, and fishing vessels only. Large ships must usetraffic lanes.

Mistake 12: Termination Area Speed

❌ WRONG: “We maintain full transit speed through the termination area because we have radar.”

✅ RIGHT: Rule 10(f) requires “particular caution” near terminations. Reduce speed, increase lookout, have engines on standby.

Part 14: Quick Reference – The 5-Minute Takeaway

Rule 9 – Narrow Channels:

Stay on the starboard side (right side) as safe/practicable

Small vessels (<20m) and fishing vessels must NOT impede large constrained vessels

Do NOT cross if it impedes a constrained vessel

For overtaking: use sound signals; get agreement; verify sea room; maintain responsibility

Sound a warning at blind bends

Rule 10 – Traffic Separation Schemes:

Follow your lane in the general direction of traffic flow

Keep clear of separation lines/zones (stay within lane)

Join/leave normally at lane terminations; if from the side, use a small angle

Cross at 90 degrees if obliged to cross (not diagonal)

Never enter separation zones except in emergencies/fishing/safety operations

Special caution at termination areas (highest danger zone)

If NOT using TSS, avoid by a wide margin

Rule 10 does NOT override COLREGS Rules 1-8; all rules apply always

Bridge Team Integration – Rules 9 & 10

For the Master:

✓ Know the narrow channels and TSS systems your ship will transit

✓ Brief the bridge team on Rule 9 and Rule 10 procedures before entry ✓ Ensure engine is readyfor rapid speed changes

✓ Expect the OOW to reduce speed and increase lookout intensity

✓ Be available on bridge during critical areas (terminations, narrow channel approaches)

For the OOW:

✓ Maintain 100% lookout (not 70-80%)—narrow channels and TSS require maximum vigilance ✓ Use radar continuously with ARPA plotting

✓ Monitor AIS for all targets

✓ Reduce speed appropriate to traffic density and visibility ✓ Sound fog signalswhen required (Rule 9f, blind bends) ✓ Document all course changes and traffic situations

For the Helmsman:

✓ Manual steering required (not autopilot) in narrow channels and TSS ✓ Stay alert for helm commands (OOW may order rapid course changes) ✓ Call out all targets and traffic

✓ Maintain constant heading as directed

For Engine Room:

✓ Maintain engine on standby in narrow channels and near TSS terminations ✓ Be ready to increase/decrease power immediately

✓ Stand by for emergency “full astern” orders ✓ Have backup power sources ready

Bridge Scenario – Integration of Rules 9 & 10

Situation: Your bulk carrier is transiting the English Channel at night, approaching Dover Strait TSS.

Current status:

Position: 15 NM from TSS entry point

Speed: 16 knots

Visibility: 2 NM (reduced due to fog)

Traffic: 40+ vessels in the TSS

Bridge procedures (applying Rules 4-10):

Rule 4 (Restricted visibility): Apply all rules strictly; heightened caution
Rule 5 (Lookout):

Post additional lookout on bridge wings

Radar on 6 NM range scanning

VHF tuned to Dover VTS

AIS is monitoring all targets

Rule 6 (Safe speed):

Reduce speed from 16 knots to 8 knots

Reason: Reduced visibility + high traffic density + narrow channel

Engine on standby

Rule 7 (Risk assessment):

Continuous bearing checks on all radar targets

AIS updates every 10 seconds

Any steady bearing = risk exists

Rule 10 (TSS entry):

Approach the termination area at 8 knots

Join the eastbound lane at a small angle (~20 degrees)

DO NOT cross other lanes

6. Rule 10 (Termination area – Rule 10f):

All bridge team on high alert

Continuous monitoring

Ready for rapid alteration or speed change

Main engine on standby (not auto standby, manual alert)

7. Rule 9 (Narrow channel principle – if applicable):

Keep on starboard side of TSS lane

Monitor for small vessels trying to cross

Result: Safe passage through Dover Strait despite challenging conditions.