Collision regulations: steering and sailing rules

The rules of the road

At sea there are no traffic lights, lanes painted on the water or police at the junctions. Instead, every vessel follows one rule book: the International Regulations for Preventing Collisions at Sea, agreed internationally in 1972 and amended several times since. Sailors call them the collision regulations, the COLREGs or simply the rules of the road. They are not advice: the UK, like most maritime nations, has made them law.

Rule 1 says they apply to all vessels on the high seas and in all waters connected to them that seagoing vessels can navigate — from the largest ship to a sailing dinghy. Harbours, rivers and inland waterways may add local rules of their own, which should follow the COLREGs as closely as possible. They are published by the harbour authority and summarised in almanacs, so check before you go.

The rules are grouped into parts. This lesson covers the heart of them, the steering and sailing rules (Rules 4 to 19). Lesson 21 covers the lights and shapes that tell you what another vessel is, and Lesson 22 the sound signals and conduct in restricted visibility. A few definitions from Rule 3 matter straight away:

• Vessel — every kind of water craft used, or able to be used, for transport on water.
• Power-driven vessel — any vessel propelled by machinery.
• Sailing vessel — any vessel under sail, provided that her engine, if fitted, is not being used. A yacht motor-sailing, with her sails up and her engine driving her, is a power-driven vessel.
• Underway — not at anchor, made fast to the shore, or aground.

Look-out and safe speed

Rule 5 says every vessel shall at all times keep a proper look-out by sight and hearing, and by all other available means, so as to make a full appraisal of the situation and of the risk of collision. On a yacht the headsail hides a large part of the view ahead and to leeward, so look under it — and look astern — regularly. Radar, if fitted, is one of the “other available means” (Module 5).

Rule 6 says every vessel shall at all times go at a safe speed, so that she can take proper and effective action to avoid a collision and be stopped within a distance appropriate to the conditions. Among the factors every vessel must take into account are:

• the visibility;
• the traffic density, including concentrations of fishing vessels;
• how manoeuvrable the boat is — her stopping distance and turning ability in the conditions;
• at night, background light from the shore or the glare of her own lights;
• the wind, sea and current, and how close she is to navigational hazards;
• her draught compared with the depth of water.

Vessels with radar must also allow for what their radar can and cannot show.

Is there a risk of collision?

The steering rules come into play when vessels approach each other so as to involve a risk of collision. Rule 7 says every vessel must use all available means to decide whether risk of collision exists, that if there is any doubt, such risk shall be deemed to exist, and that you must not jump to conclusions on scanty information.

The classic test is a series of compass bearings of the other vessel, taken with the hand-bearing compass (Lesson 11). Rule 7 says risk of collision shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change.

Steady bearing, closing range: risk of collision.

If the bearing moves steadily towards your bow, it is drawing ahead: she should pass ahead of you. If it moves towards your stern, it is drawing aft: she should pass astern. On your starboard bow, a bearing drawing ahead gets smaller; on your port bow it gets bigger. One bearing tells you nothing — take several, a few minutes apart, and look for a trend that is bigger than the degree or so of scatter in your readings.

Taking action

Rule 8 describes how to take action to avoid a collision. If the circumstances allow, it should be:

• positive and in ample time, with due regard to good seamanship;
• large enough to be readily apparent to the other vessel, by eye or on radar. A succession of small alterations of course or speed should be avoided;
• if there is enough sea room, an alteration of course alone may be the most effective action — provided it is made in good time, is substantial, and doesn’t lead to another close-quarters situation;
• such that you pass at a safe distance, checking that it is working until the other vessel is finally past and clear.

If necessary — to avoid a collision or to give yourself more time — slow down, or take all way off by stopping or going astern.

Early, substantial and obvious — then keep watching until she is past and clear.

Overtaking

A vessel is overtaking when she comes up with another from a direction more than 22.5° abaft her beam — so at night she would see only the other vessel’s sternlight, and neither of her sidelights (Lesson 2). Rule 13 says any vessel overtaking any other shall keep out of the way of the vessel being overtaken.

• Rule 13 applies whatever kinds of vessel are involved: it overrides the sailing rules and Rule 18. A yacht under sail overtaking a motor boat must keep clear of her.
• If you are in any doubt whether you are overtaking, assume that you are.
• You stay the overtaking vessel until you are finally past and clear: drawing ahead of her doesn’t turn you into a crossing vessel.

Head-on and crossing: two power-driven vessels

Rule 14 — head-on. When two power-driven vessels meet on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter her course to starboard, so that each passes on the port side of the other. It is head-on when each sees the other ahead or nearly ahead: at night, her masthead lights in line or nearly in line and/or both her sidelights. If in any doubt, assume it is head-on.

Rule 15 — crossing. 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, if the circumstances allow, avoid crossing ahead of her. The usual action is a bold alteration to starboard, passing astern — or slowing down, or both.

These two rules are for power-driven vessels only. When one of the vessels is under sail, fishing, restricted or not under command, Rule 18 (below) decides instead — and between two sailing vessels, Rule 12.

Give-way and stand-on vessels

In the overtaking, crossing, sailing and Rule 18 encounters in this lesson, one vessel is told to keep out of the way — the give-way vessel — and the other is the stand-on vessel. Head-on, neither is: both alter course.

Rule 17 adds that a power-driven stand-on vessel that takes action in a crossing situation with another power-driven vessel shall, if the circumstances allow, not alter course to port for a vessel on her own port side. That vessel is the give-way vessel, and if she wakes up at the last moment she is most likely to turn to starboard — towards you, if you have turned to port.

Two sailing vessels

Rule 12 covers two sailing vessels approaching with risk of collision. It depends on the wind. A yacht with the wind coming over her port side is on port tack, with her mainsail out to starboard; with the wind over her starboard side she is on starboard tack. Windward means towards the wind and leeward away from it (Lesson 2).

1. When each has the wind on a different side, the vessel with the wind on her port side — on port tack — keeps out of the way.
2. When both have the wind on the same side, the vessel to windward keeps out of the way of the vessel to leeward.
3. If a vessel on port tack sees a vessel to windward and cannot tell for certain which tack she is on, she keeps out of the way.

For this rule, the windward side is deemed to be the side opposite to the one on which the mainsail is carried (on a square-rigged vessel, the largest fore-and-aft sail). That settles the tack of a yacht running dead before the wind: with her mainsail out to starboard, her windward side is port, so she counts as being on port tack.

Try it: the encounter simulator

Put the rules so far together. Choose what you and the other vessel are, where she is and, if anyone is sailing, the wind. Her bearing is steady, so there is a risk of collision. Decide what you should do — then watch the manoeuvre.

Who keeps out of whose way: Rule 18

When different kinds of vessel meet, Rule 18 sets out who keeps out of whose way. In general, the more easily a vessel can manoeuvre, the more she is expected to keep clear:

• Not under command (NUC) — through some exceptional circumstance, such as an engine or steering failure, unable to manoeuvre as the rules require.
• Restricted in her ability to manoeuvre (RAM) — by the nature of her work: dredging, laying cables, servicing navigation marks, or a tow that severely restricts her.
• Engaged in fishing — fishing with nets, lines or trawls that restrict her manoeuvrability. A yacht trailing a mackerel line is not.
• Constrained by her draught (CBD) — a power-driven vessel that, because of her draught, can hardly deviate from her course in the available depth and width of water. When she shows the signals for it (Lesson 21), every vessel other than NUC or RAM shall, if the circumstances allow, avoid impeding her safe passage.

Rule 18 begins “except where Rules 9, 10 and 13 otherwise require”: the overtaking rule, and the narrow-channel and traffic-scheme rules below, still apply. And remember Rule 3: a yacht whose engine is driving her is a power-driven vessel, even with her sails up — by day she must show a cone, point downwards. Lesson 21 shows how to recognise every one of these vessels by her lights and shapes.

Narrow channels and traffic separation schemes

Rule 9 — narrow channels. A vessel going along a narrow channel or fairway keeps as near to its starboard-hand edge as is safe and practicable. A vessel of less than 20 metres in length, or a sailing vessel, shall not impede the passage of a vessel that can navigate safely only within the channel — and no vessel shall cross the channel if that would impede such a vessel. Take particular care at bends, and avoid anchoring in a narrow channel.

Rule 10 — traffic separation schemes. In busy waters, schemes separate opposing streams of shipping into traffic lanes, like a dual carriageway. A vessel using one follows the lane in the general direction of traffic flow. Avoid crossing a lane if you can; if you must, cross on a heading as nearly as practicable at right angles to the general direction of traffic flow. Vessels under 20 metres and sailing vessels shall not impede the safe passage of a power-driven vessel following a traffic lane, and may use the inshore traffic zone alongside. Vessels not using a scheme should keep well clear of it.

“Not impede” means acting early, long before any risk of collision, to leave the other vessel plenty of room. If you end up close to her anyway, the steering rules apply to both of you as well.