The Chokepoint Tracker counts the ships that pass through eight of the world's maritime chokepoints each day, sorts them by type and compares each day with the weeks before it. It is the data behind our Chokepoints issue and much of our shipping and trade coverage. This page explains what it shows, how we build it and how to use it.
What the tracker shows
For each chokepoint the tracker shows daily transits, a seven-day average and the same average four weeks earlier, split by ship type: container ships, crude and product tankers, gas carriers, dry bulk and other cargo ships. The eight passages are:
- the Strait of Malacca
- the Strait of Hormuz
- the Bab el-Mandeb
- the Suez Canal
- the Panama Canal
- the Bosporus
- the Strait of Gibraltar
- the Strait of Dover
How we count a transit
We draw a gate line across each passage at its narrowest navigable point. A transit is counted when a ship's reported track crosses that line, in either direction. We count only cargo-carrying ships of 5,000 gross tonnes or more, so ferries, tugs and fishing boats do not inflate the totals. A ship that crosses the same line twice within six hours, such as one drifting back and forth while it waits at the entrance, counts once. A ship that turns back without completing the passage is counted in the direction it finally leaves. Tracks that jump impossibly far between two reports are removed as likely errors or spoofing.
Where the data comes from
The tracker is built from AIS, the position messages large ships are required to broadcast. We buy AIS data from two commercial providers and combine their feeds: receivers on shore cover coastal waters, satellites fill in the open sea. Where a canal publishes its own daily transit figures, we compare our counts with them and investigate any gap larger than 5%.
AIS has limits. Coverage is weaker in some waters, a few ships switch their transponders off, and a small number broadcast false positions. The tracker counts what it can see. When we know a count is incomplete for a day, for example during a satellite outage, the chart shows that day hatched and the figure is excluded from the averages.
When it updates
The tracker updates every morning at 06:00 UTC with the previous UTC day. The three most recent days are marked provisional, because late satellite reports can add ships after the first count. At the end of each working week the data desk publishes a short written summary of the biggest moves.
How to cite it
The charts and the underlying daily counts are free to use with credit. Please cite Break Chokepoint Tracker with the date you retrieved the data, and link to this page where you can. Each chart has a download button for its figures as a CSV file. For larger extracts or questions about a specific day, write to the data desk through our contact page.
Changelog
Version 1.2
Added the Strait of Gibraltar and split tankers into crude and product carriers.
Version 1.1
Raised the minimum size to 5,000 gross tonnes and added the six-hour rule for double crossings, which had inflated counts at the Bosporus.
Version 1.0
First release, with seven chokepoints and five ship types.
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