Rules of the Road

Most trouble at sea is avoided long before it happens – by keeping a good lookout and knowing the rules of the road. Two things every sailor must know cold: who gives way, and what the lights you see are telling you – another vessel's, a lighthouse's, or a buoy's.

Stand-on or give-way?

In every encounter one vessel is the give-way vessel (she must take early, obvious action to keep clear) and the other is the stand-on vessel (she holds her course and speed so the other can predict her). Pick a situation:

–

Stand-on · holds course Give-way · keeps clear Wind

Who keeps clear of whom

When in doubt, the less manoeuvrable vessel has priority. Roughly, each rung gives way to the one above it:

1Not under commandBroken down – can't manoeuvre
2Restricted in ability to manoeuvreDredging, towing, laying cable
3Constrained by draughtDeep ship in a narrow channel
4Engaged in fishingNets or gear deployed
5Sailing vesselUnder sail alone
6Power-driven vesselMost motor boats & ships

Remember

Right of way is never a right to collide. Rule 2 means you must do whatever it takes to avoid a collision – including giving way when technically you are the stand-on vessel, if the other boat is not acting.

Reading another vessel’s lights

After dark, and in poor visibility, a vessel tells you what she is and what she’s doing through her lights; by day she uses black shapes. Here are the ones you’ll meet, grouped by situation – tap any row to open it. The diagrams are simple profiles (bow to the right); colours and arcs are summarised here:

White Red – port side Green – starboard Yellow – towing / special Masthead 225° · Sidelights 112.5° · Sternlight 135° · All-round 360°

Lights & lighthouses

Lighthouses, beacons and lit buoys don’t show navigation lights like a vessel – each has its own pattern. Every light on the chart carries a short code beside it, its characteristic, which packs in everything you need to identify it after dark: how it flashes, what colour it shows, how long the cycle takes, how high it stands, and how far it can be seen. Read left to right:

Fl₍₂₎WR10s24m15/12M

Fl(2) — rhythm: group-flashing, two flashes per cycle

WR — colour: white in the safe sector, red where it marks danger

10s — period: the whole cycle repeats every 10 seconds

24m — height of the light above mean sea level, in metres

15/12M — nominal range: 15 nautical miles white, 12 nautical miles red

Abbr.RhythmWhat you see

FFixedSteady, continuous light

FlFlashingDark longer than lit; a single flash each cycle

Fl(n)Group flashingn flashes, then a longer dark pause

OcOccultingLit longer than dark; a brief eclipse each cycle

IsoIsophaseEqual light and dark, on/off like a metronome

QQuickAbout 50–60 flashes a minute

VQVery quickAbout 100–120 flashes a minute – marks the most urgent hazards

Mo(A)Morse codeSpells a letter in Morse – “A” is common for safe-water marks

AlAlternatingColour changes each flash, e.g. Al.WR

Nominal vs geographic range

The nominal range printed on the chart (the “15M” above) is how far the light could be seen in clear weather, based purely on its brightness. But the earth curves away, so a light can also drop below the horizon before its brightness runs out – that limit is the geographic range, and it depends on the light’s height and your own height of eye, both in metres:

Range (nm) ≈ 2.08 × ( √(light height, m) + √(eye height, m) )

Example: a 24 m light, seen from a cockpit 2 m above the water — 2.08 × (√24 + √2) = 2.08 × (4.90 + 1.41) ≈ 13.1 nm. Whichever range is shorter, nominal or geographic, is the one that actually applies – you will raise a powerful light close to the horizon before you raise a dim one mounted high.

Buoys & beacons

Greece, and Europe generally, use IALA Region A: red to port when returning from seaward. Each mark’s shape, colour and light are designed to be recognisable even in silhouette, at night, or from a distance.

Port hand

Red · can / cylindrical

Leave to port (left) when returning from seaward. Light, if fitted, is red — any rhythm.

Starboard hand

Green · conical

Leave to starboard (right) when returning from seaward. Light, if fitted, is green — any rhythm.

North cardinal

Black over yellow

Pass to the north of the mark. Topmark: two cones point up. Light: continuous quick or very quick flashing, white.

South cardinal

Yellow over black

Pass to the south of the mark. Topmark: two cones point down. Light: Q(6) + long flash every 10 or 15s, white.

East / West cardinal

Black‑yellow‑black / Yellow‑black‑yellow

Pass east (or west) of the mark. Topmarks: cones base-to-base (east) or point-to-point (west). Light: Q(3)/VQ(3) east, Q(9)/VQ(9) west, white.

Isolated danger

Black · one or more red bands

Marks a small, isolated hazard with safe water all around it. Topmark: two black spheres. Light: Fl(2), white.

Safe water

Red & white vertical stripes

Marks a landfall or mid-channel point — navigable water all around. Topmark: single red sphere. Light: Iso, Oc or Mo(A), white.

Special mark

Yellow

Not a hazard mark — cables, spoil grounds, traffic separation, swim zones. Topmark: yellow X. Light: Fl.Y, any rhythm.

Emergencies & safety gear

Crew overboard, gear & emergencies

Crew-overboard recovery and the safety gear to carry are best learned from the bodies that train and rescue sailors, then practised on the water with an instructor. The Safety directory lists them: training and safety advice from the RYA and the US Coast Guard, plus the coast guards, search-and-rescue centres and radio-medical services to know before you sail.

* COLREGS = the International Regulations for Preventing Collisions at Sea. This is a plain-language summary for learning, not a substitute for the official rules or proper training.