To stay safe around shipping, it pays to understand the different types of marine traffic. John Lang explains all

A yachtsman’s guide to shipping


Rear Admiral John Lang, also a yachtsman, commanded two submarines and a frigate. He retired in 1995 to head the MAIB from 1997-2002

It is easy to take shipping for granted. So long as supermarket shelves are stocked and there’s fuel in forecourt pumps, the average person ashore has absolutely no interest in how goods and fuel reach us, yet every ship has a story to tell. Each contains a tiny community of people trying to do a good job in a testing environment.

The small boat sailor has a unique opportunity to see these ships relatively close up. How are they operated? What pressures do they face? How might their watchkeepers react to a small craft ahead? A little understanding about our fellow seafarers can make life more interesting and safer for us all.

Such knowledge can embrace an awareness of the routes they are likely to take, their method of keeping a lookout, an idea of speed, rate of turn, and any restrictions on their ability to manoeuvre.

Analysing traffic density


The graphics in this article are taken from the Marine Management Organisation (MMO) report Mapping UK shipping density and routes from AIS (July 2014). Conducted by ABP Marine Environmental Research using data from the Maritime and Coastguard Agency, the project tracked shipping using AIS A and B over 12 seven-day periods throughout the year between 2011 and 2012. This one shows overall UK vessel density

Most traffic from the Atlantic en route for Northern Europe, the Baltic and the Nordic countries passes through the English Channel and the Dover Strait. It is the world’s busiest waterway, averaging over 400 commercial shipping movements a day.

There is a substantial short sea trade. Dover is Europe’s busiest ferry port. Hull on the east coast, Portsmouth on the south and Liverpool and Holyhead on the west all operate ferry services to the Continent or Ireland. Product tankers, feeder container ships and small cargo ships link smaller harbours with large terminals at home and abroad.

Shipping concentrates in the approaches to our main cargo handling terminals on the Firth of Forth, Humber and Thames Estuary, the Solent, Milford Haven, the Mersey and the Clyde. Immingham is currently the UK’s largest port by volume and Felixstowe is our busiest and biggest container port. Southampton leads the way with car carriers and cruise ships, Milford Haven is the largest energy port while Aberdeen has the largest number of ship movements servicing the North Sea offshore sector.

High level of traffic

Wind farms involve a high level of support traffic. The London Array, for instance, is the world’s largest offshore wind farm with much of the support traffic operating out of Ramsgate.

Elsewhere, nearly all commercial traffic follows well defined tracks between turning points off headlands and established navigation marks, or the entry and exit points of a Traffic Separation Scheme.

Naval activity is concentrated on Portsmouth, Devonport and the Clyde with most operational sea training taking place in designated areas to the south and south-west of Devon and Cornwall, and in the north-west approaches to the British Isles.

Small day fishing boats are ubiquitous but larger British- and EU-registered vessels will be largely confined to Scottish waters and in the south-west. The UK’s leading fishing port is Peterhead, followed by Lerwick and Fraserburgh. Brixham is England’s premier fishing port, ahead of Plymouth and Newlyn. Once at sea, a fishing vessel’s actual path will be determined by where the skipper judges the next catch to be or his pots have been laid.

Tracking traffic yourself


As part of your passage planning, you can check online to find out what shipping to expect on passage

To accommodate or avoid traffic while passage planning, use AIS websites such as or AIS is not infallible. Some vessels may not feature, some information may be inaccurate, but the broad picture of shipping concentrations can be seen in the comfort of one’s home.

Cargo ships and tankers


Routes are well defined, particularly in the Channel and Dover Strait. Cargo ships have more short sea trade

Most large container vessels operate to a pre-determined schedule carrying, mainly, manufactured goods. They have largely replaced traditional cargo vessels with their holds and derricks. They also get bigger with every passing year and some are capable of capable of carrying 18,000 TEU (the standard container is 20ft long: the Twenty Equivalent Unit) and larger vessels are planned. China Shipping Container Lines (CSCL) recently agreed to lease six 21,000 TEU ultra-large container ships currently in build.


Container ships can be 400m long and usually make 15-20 knots

Only a few UK terminals, such as Felixstowe and London Gateway, can handle the largest container ships but many others including Southampton, Tilbury and Gourock handle the slightly less large vessels every day. Smaller container vessels, or feeder ships, are regular callers at a range of coastal ports, connecting them to large terminals. Among the busiest cargo ships afloat, their crews are most likely to be tired.

Container ships can make over 20 knots but, increasingly, opt for 15-20 knots to contain costs and meet ever more stringent environmental standards. They tend to be highly automated.

With very high freeboards and numerous decks, car and vehicle carriers earn few accolades for good looks but can transport 4-5,000 cars or more. They keep precise schedules and, like small container ships, can load or discharge within 24 hours.


Bulk carriers draw up to 20m and, when loaded, alter course slowly

Dry bulk carriers, or bulkers, carry raw materials: iron ore, coal, grain, bauxite, salt, phosphates, biomass or wood pellets and cement. Both large ocean-going bulkers and small coastal ones spend more time in harbour discharging and loading than most trades. Smaller vessels may visit lesser-known British ports with cargoes of building materials, fertiliser or forest products, while large ones stick to the main shipping lanes bound for their port of discharge, such as Immingham or Avonmouth. A single screw propels them at 11-16 knots and, when laden, they may be constrained by a draught of up to 20m. They are not the most nimble of ships, and can be slow to alter course when giving way.


A full crude carrier has a draught of up to 30m, restricting manoeuvrability in narrow shipping channels near ports

Liquid carriers vary from smaller product tankers to huge crude oil carriers that are now infrequent visitors to these shores – they tend to head for Rotterdam or Wilhelmshaven instead. They can be 400m long or more, with draughts over 30m, significantly constraining their ability to manoeuvre in the Dover Strait and the North Sea.

Gas carriers have special tanks to carry liquefied gases under pressure at very low temperatures, to terminals at Milford Haven and the Isle of Grain. A large gas carrier may reach 20 knots and draw around 12m.

Passenger vessels and high speed craft


High speed craft stick to clearly defined routes, likewise large ferry traffic. Cruise ships, often found in tourist hotspots like the Scillies and Western Isles, will resist sharp course alterations

Passenger carrying vessels fall into two main categories; cruise ships and ferries. With the single exception of the Queen Mary II, the ocean-going liner of yesteryear has passed into history.

Cruising is the fastest-growing sector of the maritime world. As elsewhere, economy of scale dominates and many new cruise ships are vast with most cabins enjoying a sea view. The UK features a number of cruise terminals such as Southampton, Dover, Tilbury, Bristol and Liverpool, with a number of other ports enjoying this facility. Cruise ships visit other places, like the Isles of Scilly and the Western Isles, as part of a cruise around these islands. Cruise ships tend to spend the day in harbour and steam at night, which means the daysailing yachtsman tends not to see them except in the late afternoon and evening, or if they happen to be under way in the vicinity of a terminal port or a place being visited.


Ferries may sail at 25-27 knots on well defined routes, with European officers keeping watch

Ferries ply regular routes all round the coast providing services to the Northern and Western Isles, the near Continent, the Channel Islands, the Isle of Wight, the Isles of Scilly and Ireland. Some are large and fast. Brittany Ferries’ Pont-Aven, for instance, links Portsmouth with Santander in Spain, has a gross tonnage of 41,700 tons and cruises at 25-27 knots.

Cruise ships and ferries are among the most manoeuvrable vessels in British waters. They are the only ships likely to have British or European officers of the watch. Ferry watchkeepers are likely to be very familiar with small-boat sailors as they ply fixed routes on well-established schedules. Their movements are probably the most predictable of any ship encountered and they should expect small craft to keep out of their way when entering or leaving harbour.

Cruise ships on passage keep very good lookouts and rely on early decision making if it becomes necessary to give way to another vessel. Passage speeds are not that high, perhaps 16-22 knots, but large wheel angles for last-minute course alterations are not encouraged. A big cruise ship with her high freeboard and relatively shallow draught will begin to heel if a large rudder angle is applied. Large angles of heel are not conducive to passenger comfort, or the peace of mind of company lawyers.

The ferry sector includes the high-speed catamarans operated by Brittany Ferries, Irish Sea Ferries and Condor, sailing on well-defined routes. They tend to use their high speeds of 35-40 knots to avoid close-quarters situations but a good lookout for them is still essential. In poor visibility they can often be heard before they are seen.

Fishing vessels and service boats


Fishing vessels will not follow defined routes, they go wherever the fish take them, while pilot boats, wind farm support vessels and dredgers rarely venture far from port

Inshore fishing occurs almost anywhere in coastal waters: we’re all familiar with the half-submerged buoy marking the end of a chain of pots. Encounters with larger vessels are rarer, except when they set out or return to land their catch trailing a flock of seagulls and an unmistakable smell.


A trawler heads offshore from Lerwick, her deck working lights blazing through the dusk

Fishing has three sectors; pelagic, demersal and shellfish. Each involves different techniques and locations, depending on the time of year, quota allocations and weather.

Pelagic fishing catches fish near the surface like herring, mackerel, sprats and whiting. Mackerel migrate from the spawning areas west of Ireland from March to July to the North Sea for the winter. Herring, less mobile, are found west of Scotland and in the North Sea. Pelagic trawlers operating out of Shetland and the Moray Firth ports are among the largest and most profitable fishing boats. Craft using drift nets target smaller herring fisheries elsewhere.

Demersal fish, on or near the seabed, are caught with 5-80m long nets towed behind trawlers. Larger vessels haul their catches up a stern ramp, smaller ones over the side. Fish are processed by the crew and stored in chilled holds before being landed. Given the high cost of marine mortgages, fuel and equipment, coping with bad weather and finding crew, it’s a tough industry.


Coastal fishing boats are smaller and operate with just one or two crew

Fishing boats encountered at sea are either on passage to and from the grounds, engaged in fishing or, in bad weather, hove to. Speeds vary from near stopped to 3-5 knots while trawling, and between 8-15 knots or more on passage. Fishing boats at night often display bright deck working lights, which makes them very visible but can detract from their ability to see you.

Except for the large, grey-painted Royal Fleet Auxiliary vessels that operate very closely with the Royal Navy, most support and service vessels are relatively small. They are normally encountered in harbours, port approaches and coastal waters, or servicing offshore oil and gas platforms. They include vessels that tend buoys and light vessels, or are engaged in dredging, towing, the offshore sector, fishery protection, surveying and research.

On encountering a vessel that doesn’t appear to be on passage anywhere, those on watch should look for signals, lights or shapes that indicate she is restricted in her ability to manoeuvre or is performing a specific task, and act accordingly.

Many service boats, particularly pilot launches and wind farm support vessels, propel at quite high speed and are highly manoeuvrable. They also operate in well-defined areas.

What cruisers need to know


You’ll see them before they see you, and you have better manoeuvrability. Your safest bet is to keep clear

When under way in the vicinity of commercial shipping, the small craft’s overriding priority is to remain safe. Avoid impeding the progress of larger vessels in situations that may include crossing a busy shipping lane, meeting in a narrow channel or sharing the same congested stretch of water. The need to maintain a good all-round lookout is fundamental to sound seamanship and, given good visibility and a moderate sea state, the cruiser’s low vantage point will almost always mean they will see a large vessel before the big ship sees them. A ship’s hull silhouetted against the skyline by day and the bright navigation lights of power-driven vessels by night give the small boat sailor time to determine if risk of collision exists.

The Collision Regulations thereafter determine the appropriate action to be taken. If avoiding action is necessary, every experienced sailor will be familiar with the need to ensure it is made in good time, that it is substantial, readily apparent to the other vessel and made well before a close-quarters situation arises. Most merchant ships proceed at speeds that vary from as little as 8 knots to about 16, but some go much faster. A modern container ship could for instance be propelling at 20 knots or more and this can mean that the time taken to cover the distance from the apparent horizon to being worryingly close is no more than about 12-15 minutes. Keeping a good lookout is not just confined to the initial detection but at all times thereafter until any risk of collision is over. Merchant ships will alter course to navigate safely, and anticipating such alterations comes with experience as well as local knowledge.

View from the bridge

Whilst assessing what action, if any, needs to be taken, the small-boat watchkeeper can benefit from understanding what their opposite number on the bridge of the larger ship is having to cope with as they go about their normal business.


The officer on watch keeps a visual lookout for close-quarters pilotage. At sea, that probably won’t be the case

Except when under way in pilotage or congested waters, the big ship officer of the watch (OOW) will, most likely, be alone on the bridge with both steering and propulsion in automatic control. This means they are dealing with navigation, reacting to alarms, monitoring onboard mechanical and electrical systems, dealing with incoming signal traffic and navigation warnings, as well as maintaining a good lookout using every means available. Despite its importance, looking out of the window is not always the top priority.


Watchkeeping on passenger ferries and cruise ships is very good, not always the case on hard-pressed vessels engaged in the short sea trade

Most professional seafarers do their best to carry out their duties conscientiously but, given the economics of the industry, unfortunately they can be hard pressed to do so. Some owners are forever looking for ways to cut costs in a fiercely competitive industry, and quite often they do so by reducing manpower to the absolute bare minimum.

This can mean that those on board, including the bridge watchkeepers, don’t get the rest they need to perform their duties satisfactorily and, over time, become very tired. It is particularly prevalent in the short sea trade. Ships are supposed to have a dedicated lookout at night in addition to the OOW but, judging by the findings in numerous marine accident investigation reports and declarations made in confidential reporting schemes, they are often absent from the bridge with a consequent reduction in the efficiency of the lookout.

Detecting a small craft from the bridge of a merchant ship is reasonably straightforward but becomes progressively more difficult in grey, murky conditions with a sea running. Detecting the relatively dim navigation lights of a small craft at night and in good visibility is reasonably assured, but picking out a white masthead light against a backdrop of shore lights can be a challenge as can detecting the stern light of a small vessel in a rough sea. Merchant ship watchkeepers rely increasingly on their radars and AIS for both detecting other vessels and determining whether risk of collision exists. Visual correlation with such contacts may be cursory.

AIS and radar improve your ability to keep a lookout. An AIS transceiver and active RTE ensure your presence is known by marine traffic


AIS and radar improve your ability to keep a lookout. An AIS transceiver and active RTE ensure your presence is known by marine traffic

Modern radars are far better at detecting small craft than in days gone by but are not infallible. Enhancing one’s radar echo with a proven radar reflector or, better still, an active RTE (radar target enhancer) is a sound investment in a small craft, as is the installation of Class B AIS. It may also be worth checking that all navigation lights comply with the relevant regulations.

Should you hail on VHF?

Whilst hesitant to recommend that small craft should avoid communication with a merchant ship on VHF to determine the other’s intentions, it should be remembered that such calls can add to the merchant ship’s problems. Except when under way in VTS (Vessel Traffic Services) waters, there is every probability that there is only one person on the bridge and such a call can be a distraction. A merchant ship under way in VTS waters is probably better placed to take a call but it then becomes essential that any exchange of navigation or intention information is made on the VHF Sector channel so that everyone listening in, including the VTS watch officer, knows what is happening.

It goes without saying that a sound understanding of the Collision Regulations goes a long way to ensuring the safety of all at sea. Of all the rules that might vie for primacy – and there are many – the one that most stands out for the small boat sailor’s interaction with other shipping is the imperative of keeping a good lookout at all times. And the philosophy that should guide their actions when in the vicinity of large vessels is to avoid, where possible, getting into situations that might impede their progress in narrow channels and coastal waters. We share the seas with others. Let’s enjoy their company and return home safely.