Safe Speed and the Lookout Rule: The Foundation of Collision Avoidance

Ask any accident investigator what causes most collisions at sea and the answer rarely involves an exotic misreading of the give-way rules. Far more often it comes down to two basics: someone was not keeping a proper lookout, or someone was going too fast for the conditions. These two duties, set out in Rules 5 and 6 of the COLREGs, apply to every vessel at all times, and they underpin every other rule in the book. You can know the give-way hierarchy perfectly, but if you never spot the other vessel, or cannot stop in time, none of it helps.

This guide explains what a proper lookout really means, how the COLREGs define safe speed, and the factors you must weigh when deciding how fast to go. These are foundational exam topics precisely because they are foundational to safe boating.

Rule 5: Keeping a Proper Lookout

Rule 5 requires every vessel to maintain a proper lookout by sight and hearing as well as by all available means appropriate to the circumstances, so as to make a full appraisal of the situation and the risk of collision. Read that carefully, because each phrase carries weight.

“By sight and hearing” means using your eyes and ears constantly, scanning the whole horizon, not just staring ahead. Sound matters too; you may hear another vessel’s engine or fog signal before you see it. “By all available means” extends the duty to any equipment that helps, such as radar or AIS if fitted, and in restricted visibility using radar properly becomes part of a proper lookout. The lookout must be maintained “at all times,” not just when you think there is traffic about.

Crucially, the lookout must be someone genuinely watching. On a small boat the helmsman may be the lookout, but if the helmsman is distracted, navigating below, or the workload is high, a dedicated lookout may be needed. The most common single cause of collisions is a failure of lookout, so this rule is not a formality; it is the front line of safety.

Rule 6: Proceeding at a Safe Speed

Rule 6 states that every vessel must at all times proceed at a safe speed, defined as a speed that allows it to take proper and effective action to avoid a collision and to stop within a distance appropriate to the prevailing circumstances and conditions. There is no fixed number; safe speed depends on the situation, and the same vessel may have very different safe speeds on a clear open day and in a crowded, foggy channel.

The rule then lists factors every skipper must take into account when judging safe speed. For all vessels these include:

• The state of visibility.
• The traffic density, including concentrations of fishing or other vessels.
• Your vessel’s manoeuvrability, especially its stopping distance and turning ability.
• At night, the presence of background light such as shore lights that can mask navigation lights.
• The state of wind, sea and current, and the proximity of navigational hazards.
• Your vessel’s draught in relation to the available depth of water.

Vessels with radar have additional factors to consider, relating to the equipment’s characteristics and limitations. The point of the list is that safe speed is a judgement, and a skipper is expected to make it deliberately rather than simply travelling at whatever speed feels comfortable.

How Lookout and Safe Speed Work Together

These two rules are partners. A good lookout gives you early warning of a developing situation, and a safe speed gives you the time and room to do something about it. Together they create the margin that every other rule relies on. The give-way and stand-on rules assume you have seen the other vessel in good time and can manoeuvre; strip away lookout and safe speed, and those rules have nothing to work with.

Consider fog. As visibility falls, a proper lookout increasingly depends on radar and hearing, and safe speed must come down so you can stop within the distance you can effectively assess. A skipper roaring through fog at open-water speed has broken both rules at once, and in the eyes of any inquiry has behaved recklessly regardless of who technically had right of way.

Practical Habits That Satisfy the Rules

Turning Rules 5 and 6 into daily practice is straightforward once you build a few habits.

• Scan the whole horizon regularly, including behind you, since overtaking traffic comes from astern.
• Check whether the bearing to another vessel is changing; a constant bearing with reducing range means a collision risk.
• Reduce speed early when visibility drops, traffic thickens, or you enter unfamiliar or shallow water.
• Make sure someone is always actually watching, and share the lookout task on longer passages so nobody becomes fatigued.
• Use radar and AIS to supplement, never replace, your eyes and ears.

None of this is complicated, but doing it consistently is what separates safe skippers from the statistics.

Getting It Right on the Exam

Examiners test Rules 5 and 6 because they are the bedrock of collision avoidance, and questions often ask you to identify the factors affecting safe speed or to recognise a lookout failure in a scenario. The concepts are logical rather than fiddly, so a little focused practice cements them quickly. In the boatingexamine course you can work through lookout and safe-speed questions in exam format, so you can recall the factors and apply them confidently when it counts.

FAQ

Is there a specific safe speed in knots I should remember? No. The COLREGs deliberately avoid a fixed number because safe speed depends on conditions. It is the speed at which you can take effective action and stop in an appropriate distance given visibility, traffic, manoeuvrability and other factors. Local harbour bye-laws may impose specific limits on top of this.

Who is responsible for keeping a lookout? Every vessel is, at all times. On a small craft the helmsman often doubles as lookout, but if workload or conditions demand it, a dedicated lookout must be posted. The duty covers sight, hearing and all available means such as radar where fitted.

Why is safe speed so important in fog? In restricted visibility you can only assess what is close to you, so you must be able to stop within that distance. Reducing speed gives you the time to detect vessels, judge the risk, and take avoiding action. Excessive speed in fog is one of the clearest breaches of the collision regulations.