What do international anti-collision regulations for ships have to do with whales? And why for heaven’s sake are there “highways” in the open sea?

Michael Barbaix

17 hours ago

6 min read

In this article, I, Capt. Michael Barbaix, will explain why whales and the “rules of the road” for ships can be a blessing for each other, and why sometimes they “collide” (blink, blink, blink) with each other…

First, a bit of history.

Ships have been navigating the world’s oceans for centuries. But as maritime traffic became busier, simply giving every vessel the freedom to sail wherever it wanted was no longer sufficient. After multiple head-on ship collisions in the busy waters of the English Channel, the first so-called Traffic Separation Scheme (TSS) was developed in 1967 in order to regulate shipping traffic. The landmark COLREG (Collision Regulations) Convention of 1972 subsequently incorporated the concept into international collision regulations.

Rule 10 defines the conduct of vessels operating in or near a TSS.

These Traffic Separation Schemes are commonly known as "highways of the open sea". To an untrained eye looking out from the cliffs of Dover, there may appear to be ample room for any and all ships. But a trained navigation officer will look at these waters with the necessary caution they deserve. A TSS generally consists of two traffic lanes, which are basically two one-way traffic corridors, separated by a separation line or zone. The separation line or zone acts as a buffer between the two opposing traffic directions.

Rule 10 requires vessels using a traffic separation scheme to follow the prescribed traffic flow and, as far as practicable, keep clear of the separation line or zone. Ships crossing the lanes should do so as nearly as practicable at right angles to the general direction of traffic flow. The idea is beautifully simple: instead of everybody sailing wherever they please, traffic is organised into predictable streams.

And it works.

The International Maritime Organization (IMO) reports that the number of collisions in the Dover Strait fell substantially after the introduction of traffic separation. Today, the IMO has adopted nearly 200 traffic separation schemes around the world, while individual countries have also established local routeing measures under their national frameworks.

So far, so good.

But what does all of this have to do with whales?

Quite a lot, actually.

The problem with a highway that has no fences

Unlike a road on land, a maritime highway has no physical barriers. At sea, the “road” is an imaginary purple line on a nautical chart. Whales have absolutely no interest in COLREG Rule 10 nor an imaginary purple line in the water. They do not recognise a traffic lane and they do not understand the concept of a separation zone.

They have no idea that the large object approaching them at 15 knots (~ 28 km/h) is a container ship with a cargo of 24,000 containers, a very large propeller AND a bridge team that would very much prefer not to run over them. This creates a problem because some of the world's busiest shipping routes pass through, or close to, important whale habitats.

And this is where maritime safety and whale conservation start to intersect.

Can we move the highway?

If a road repeatedly causes accidents at a particular location, one possible solution is to move the road. At sea, we can do something similar.

A TSS is not a permanent feature of nature. It is a navigational management measure. Existing routeing schemes can be amended when circumstances change, and new routeing measures can be proposed through the IMO system. One particularly interesting example is the Traffic Separation Scheme serving Boston. The waters around Massachusetts are important habitat for North Atlantic right whales, while Boston is a major commercial port. That means there is an unavoidable overlap between whale habitat and a substantial amount of commercial shipping.

In 2007, after extensive work involving NOAA, the U.S. Coast Guard and other parties, the Boston shipping lanes were modified. The lanes were shifted to the northeast and narrowed, moving large-vessel traffic away from areas where concentrations of right whales were found.

This is a beautiful example of how an instrument originally developed for maritime safety

can also become an instrument for environmental protection. It is that maritime routeing can respond to environmental information when there is sufficient evidence of a recurring conflict between vessel traffic and sensitive marine areas. Similar examples of a TSS redesigned for whale protection exist in San Francisco and Panama.

Of course, changing a TSS is not always the answer. Depending on the location and the characteristics of the whale population, other measures may be more appropriate - for example seasonal measures, recommended routes, areas to avoid, or speed reductions.

The key is having reliable information about where and when the risk occurs.

A closer look at the South African Coast

This distinction becomes particularly relevant when we look at the complex waters around South Africa, where changing shipping patterns are increasing the importance of understanding the interaction between maritime traffic and whale habitat.

There are two IMO-adopted Traffic Separation Schemes situated well offshore: one 47 nautical miles (87 km) south of Mossel Bay, in the vicinity of the FA platform, and another 34 nautical miles (63 km) south of Cape Infanta, off the Alphard Banks.

These are interesting TSSs because they are not approach schemes for a port. They are there specifically to organise through traffic along the South African coast. In that respect they are comparable to the TSS of Dondra Head, south of Sri Lanka, where the principal purpose is also to guide vessels making an international transit rather than vessels approaching a particular harbour.

There is an important legal and practical distinction here.

These schemes lie outside South Africa's 12-nautical-mile territorial sea. Consequently, they are not simply a matter of a coastal state drawing lines on a chart and declaring them to be mandatory. The routeing measures have been submitted to and adopted by the IMO. As a result, any significant amendment to these internationally adopted schemes has to follow the appropriate IMO procedure.

Closer to the coast there are three locally adopted TSS, serving the approaches to Cape Town, Saldanha Bay and Port Elizabeth.

These are a rather different proposition. They are associated with the approaches to South African ports and fall under the national regulatory framework. Durban and Richards Bay, interestingly, do not have an approach TSS of this type.

For the navigator, this distinction may seem like a technicality. A line on the ECDIS is a line on the ECDIS, after all. But from a regulatory and environmental point of view, it can be extremely important. If a particular TSS is identified as a problem for whales, for example, the question is not simply: “Can we move the line?” The first question is: who has the authority to move it, and what procedure has to be followed?

For a locally established scheme, the coastal state has considerably more scope to make changes within its own regulatory framework. For an IMO-adopted international routeing measure, the process is more formal and involves the international community through the IMO.

And this brings us back to the central theme of this article: a TSS may look like nothing more than two lines and a separation zone on a nautical chart. In reality, those lines represent an entire framework of international and national law, navigation practice, maritime safety and, increasingly, environmental management.

Why is this particularly important now?

Recent changes in global shipping patterns have increased vessel traffic around the Cape of Good Hope. As reported by Mongabay in June, rerouting around southern Africa following disruptions to shipping through the Red Sea has resulted in a significant increase in large-vessel traffic in the region.

According to satellite data cited in the article, between December 2023 and December 2024, the number of large vessels travelling through South African waters at average speeds above 15 knots has quadrupled. At the same time, Southern Hemisphere spring brings large aggregations of whales to parts of the region.

"During the Southern Hemisphere spring, particularly between October and

November, so-called supergroups - aggregations of between 20 and hundreds of whales feeding together - gather in the Benguela Upwelling System, one of the world’s most productive ocean ecosystems."

More whales and more ships occupying the same waters can mean a higher collision risk.

And when whales aggregate in large numbers, a single ship strike can potentially affect multiple animals.

One of the most important measures would be speed restrictions like the 10-knot (18.5 km/h) limit in force along the U.S. East Coast to reduce strikes with North Atlantic right whales.”

From maritime highways to whale-aware navigation

There is already a growing amount of whale information available around the world. The challenge is turning all this information into something that can actually be used by the maritime industry.

At Whale Guardians, we work on bringing whale-sensitive areas and relevant whale data into a format that can be integrated into existing maritime and voyage-planning systems. The aim is not to tell every ship where it can or cannot sail. It is to provide navigators and voyage planners with better information about where whale collision risk may be higher, so that appropriate measures can be considered early enough to make a practical difference.