What Is the "strait" of Hormuz?#2
“Couldn’t ships simply avoid one another on their own in the open sea?” one might think.
But if we imagine a situation in which 300,000-ton oil tankers freely navigate while each pursuing only the shortest route, the sea would soon be burdened with high uncertainty and a serious risk of collision.
Even a slight error in predicting which direction another vessel will maneuver to avoid danger can place large ships—whose stopping distance and turning performance are limited—on a collision course within a short time.
So human beings created rules even on the sea.
It is a systemic agreement designed to reduce the cost of uncertainty. By partially restricting everyone’s freedom of movement, it paradoxically secures more predictable and safer navigation.
One of those systems is the TSS.
The waters of the Strait of Hormuz may look wide, but in reality the navigational space that commercial vessels can use freely is far more limited.
Many congested straits manage the flow of ships through a Traffic Separation Scheme, or TSS. It is a way of establishing something like invisible lanes on the sea.
One lane is only for ships coming in.
The opposite lane is only for ships going out.
And between them lies a separation zone intended to reduce the risk of collision.
In the Strait of Hormuz as well, this structure appears relatively clearly.
The inbound route and the outbound route each have a width of about 2 nautical miles, with a central separation zone lying between them.
In other words, even though it looks like a wide sea, the actual flow of large commercial vessels is aligned and moves within a width of roughly 6 nautical miles.
Then who designs and adopts this invisible highway?
At the center of it is the International Maritime Organization, the IMO. But the IMO does not draw the lines on its own. The actual traffic system is internationally adopted through proposals and consultations by the coastal states.
In Hormuz, this is where legal tension arises.
In the narrow parts of the strait, ships pass through the territorial waters of Iran and Oman. International law contains principles concerning straits used for international navigation, but in actual Hormuz those principles are not always applied in a simple way.
Iran and Oman have each shown their own positions regarding national security and passage.
In an ideal case, the TSS functions as a kind of management mechanism.
Under the adopted traffic system, the coastal states seek to maintain navigational safety and jurisdictional order, while ships seek to reduce the risk of collision and political friction by following those rules.
In other words, the TSS can be seen not so much as a mere lane system, but as a shared operational rule through which different interests secure a minimum level of predictability.
Now let us imagine that we are operating a very large crude carrier.
It is a supertanker departing from inside the Persian Gulf, passing through the Strait of Hormuz, and heading out into the Gulf of Oman.
It is about 380 meters long, has a deadweight of around 300,000 tons, and is carrying about 2 million barrels of crude oil. If we assume 100 dollars per barrel, the cargo alone is worth about 200 million dollars.
Our ship enters the outbound lane.
Its speed has been reduced from 15 knots—about 27.8 kilometers per hour—to around 10 knots, about 18.5 kilometers per hour.
Ahead of us in the same lane, another tanker is visible, and beyond the separation zone, in the opposite lane, another large vessel is passing.
A ship of this size cannot change direction suddenly like a car.
Turning requires a large amount of space, and this vessel has a turning radius of about 1.5 kilometers. In a narrow passage, making a sharp change of direction is practically impossible.
Once wind and current are added as factors, engine output and rudder angle must be adjusted continuously in fine increments.
And at last, the moment we emerge from the strait, the view opens wide, and the Gulf of Oman spreads out before us.