Collision Avoidance


Going boating and not sure how to avoid a collision? Applying the rules is a good start …

Just over two months ago, on a Mother’s Day fishing trip southwest of Darwin, a woman used her body to shield her children from an oncoming boat that crashed into theirs. The woman and her two children were seriously injured and flown to Royal Darwin Hospital. Water Police detectives are investigating the incident.

How could it happen? This is not an isolated event – collisions occur on the water all too frequently.

The International Regulations for Preventing Collisions at Sea (Colregs) provide the on-water ‘rules of the road’ and form the basis for orderly boating, no matter where you’re boating. The regulations apply to coastal waters, bays and inland waters, and all boat skippers should know them well.

But do you really know the wider obligations that the collision regulations place on you?

The concept of having an absolute ‘right of way’ does not apply on the water. On roads, there are lanes, give way signs, traffic lights, speed limits and advisory signs, which are all designed to enable orderly and safe progress between vehicles. On the water, however, these aids don’t exist – it’s the understanding and application of the rules, based on your judgement, that drive safety between vessels.

The words ‘give way’ do not appear regularly in the collision regulations and, if a collision occurs, it is possible that some blame will be apportioned to each vessel. The rules are based around keeping out of the way or not impeding another vessel – this is a subtle, but very important difference to claiming a right of way. The rules are also quite specific about it being everyone’s responsibility to avoid collision.

There are two important concepts that must be embraced before any thought is given to who avoids who and in what situation: keeping a lookout, and travelling at a safe speed.


The rules require every vessel to maintain a proper lookout by sight, hearing and other available means, such as radio and radar. The purpose of this is to make a full appraisal of the surrounds and assess the risk of collision. Boats can approach from any angle, including overtaking from behind, so develop the habit of scanning all around. Chartplotters and GPS units often create a distraction from a proper lookout – don’t fall into the trap of focussing on them alone.


Skippers must travel at a safe speed relative to the circumstances being encountered. A ‘safe speed’ is a speed that will allow you to assess the risk of collision and be able to take timely action to avoid it.

Conditions that will dictate a safe speed include visibility, sea state, density of traffic, vessel manoeuvrability and, at night, the presence of background lighting.

Don’t confuse safe speed with state law for statutory speed limits, such as five knots within 50m of other vessels and so on, which work side-by-side. A knowledge of all statutory speed limits is essential, as is an appreciation of what constitutes a safe speed where speed limits aren’t imposed.


Those who have a boat licence should be familiar with the basic rules, but it’s always a good idea to refresh memories.

Powerboats, including personal watercraft (PWCs), must not impede boats under sail, rowboats, canoes and other human-powered craft.

In narrow channels and rivers, keep to the right.

When meeting head-on, power-driven vessels should both alter course to starboard (their right).

When overtaking, keep clear of the vessel you are overtaking – you may overtake on either side providing it is safe to do so. The vessel being overtaken should maintain course and speed.

When crossing, the vessel with the other on its starboard (right) must not impede the vessel that’s on its starboard. In other words, you avoid the vessel on your right.

Let’s look at some of these regulations in more detail. Meeting another vessel head-on is self-explanatory, but what does crossing and overtaking mean?

Think of a circle drawn around your boat and split into segments. Imagine segments from straight ahead, going to both the right (starboard) and the left (port) until 112.5 degrees (that’s just past the perpendicular). If you’re approaching another boat from within these segment arcs, you are crossing, which means the crossing rules apply and you have to avoid the vessel approaching from your starboard side.

At night, the port and starboard lights shine over these zones, as does the white masthead light that indicates the boat is power driven. The remaining area behind the crossing zones is the overtaking zone – it covers the last 135 degrees and, at night, you would see only the white stern light.

Additionally, there are special rules relating to vessels under sail. The very nature of sail power often tempts skippers to wait until the last moment to take avoiding actions so they can get the maximum benefit of the wind. While there are many excellent yachtsmen on the water, there is no way of telling who is who, and close-quarters sailing can elicit unpredictable results. If you consider yourself to be experienced or to have good seamanship skills, then there is no place for leaving actions to the last minute for the sake of getting a bit more clean air.

When sailing boats have the wind on different sides to each other, the vessel with the wind on its port side keeps out of the way of the other. If you cannot be certain that an upwind boat has the wind on its port side, you should avoid it. If sailing boats both have the wind on the same side, the windward boat keeps out of the way of the leeward boat.


So how does all this work? Remember, the lookout’s role is to determine the risk of collision, so you should have your head ‘on a swivel’ and looking all around at all times to check for other boats and other obstacles.

If the relative bearing of an approaching vessel doesn’t change, you are at risk of a collision. If you are unsure, assume you are on a collision course.

When required to avoid another boat, take positive steps early and when altering course, make it large enough so the other boat knows you are taking avoiding action. Use your boat as an indicator. Slow down or alter course to pass behind the other boat, don’t speed up to pass in front – it is not safe and could be considered negligent.

If another vessel has to avoid you, maintain your course and speed. Only deviate if it is apparent that the other vessel is not taking action to avoid a collision. Don’t alter course to port as they may alter to starboard at the last moment and you may collide. Slowing down or stopping is a good strategy.

Ships in channels and fairways have priority – and must be avoided. An early indication that you are avoiding them is important. You may be difficult to see from the bridge of a ship, so stay clear and take early and obvious avoiding action if needed.

Light It Up

The Colregs also specify what lighting is required on boats. This is a whole topic in itself, but it’s imperative to understand what lights mean in regard to collision regulations. And if you operate a boat at night, you must display the correct lights.

Signal combinations of black spheres, diamonds or triangles – called day shapes – are also outlined in the regulations. The most common seen by small craft are the dredging signals.

Sound signals are, likewise, covered in the rules – they’re used to indicate when vessels are manoeuvring, or to assist with location for collision avoidance when visibility is restricted.

Two sound signals that should be known are three short blasts, and five short blasts. Three indicates the vessel is putting its engines astern (this does not necessarily mean the vessel is going backwards, though, but you should be alert for that to occur).

Five short blasts means “I do not understand your intentions.” This signal is commonly used by ships to alert boats of their presence and indicates that they do not understand what you intend to do. If you hear five short blasts and believe it applies to you, make your intentions clear by moving your boat to indicate you are avoiding the vessel. In restricted visibility, including fog, vessels underway sound one long blast every two minutes.

Depending on where you are boating, there may be local rules, including for direction of travel on confined waterways. These should be observed in conjunction with the collision regulations.


An Automatic Identification System (AIS) is mandatory for large vessels and is becoming increasingly popular on smaller boats. AIS devices transmit details about a vessel, including its identity, speed, course and position. Other vessels fitted with AIS can read this information on their electronic navigation systems, with the technology also projecting courses of the transmitting vessels, which helps an observer predict collision possibilities. AIS provides a live map of vessels equipped with the technology.

There are two types of AIS systems: Class A and Class B. Using VHF radio signals, Class A systems have reserved slots in the AIS system, whereas the Class B systems search for and use available slots. While position updates from Class B systems may be slower, they’re suitable for recreational craft. Cheaper ‘transit only’ sets are also available.

With AIS, you will always be visible to larger vessels and others equipped with AIS. In emergencies, your position is immediately known, while in congested waterways, high traffic areas and low visibility, AIS assists in developing an overall picture of vessel traffic – but remember: not all vessels are equipped with AIS, so proper lookout remains essential.

As a component of your boat’s equipment, AIS systems are relatively inexpensive in relation to the overall cost of your boat – depending on your boat’s set-up, expect to pay between $700 and $2000.

As a final point, breakdowns in observing collision regulations can cause frustration, right down to causing death. In 2014, a boat collision on a Victorian lake resulted in the tragic death of a 12-year-old girl. It was reported that police were investigating whether speed, afternoon glare and distractions of waterskiers may have contributed. A man was subsequently charged with, and convicted of, an offence against the collision regulations. It need not have happened.

While working with the Water Police, I often had to ask a skipper what their reason was for failing to keep a proper lookout and travelling at a safe speed … not a pleasant task, as it invariably meant someone had been involved in a collision.

Nobody wins in a collision! Collision avoidance is much more than just ‘giving way’ so, before your next trip, brush up on the collision regulations, get to know the finer details, and put them into practice.

Happy and safe boating.

How to-Safety