Traffic Separation Scheme (TSS)

The Traffic Separation Scheme through the Strait of Hormuz is the internationally recognised maritime corridor, administered under IMO conventions, that separates inbound and outbound tanker traffic through the strait. It carries approximately 20% of global oil supply and is one of the most closely monitored shipping lanes in the world. On 9 April 2026, the IRGC published danger zone charts via ISNA and Tasnim overlaying the TSS with a maritime exclusion area, effectively declaring the standard lanes hazardous and directing ships instead towards Larak Island corridors under IRGC escort.

The TSS was established under the International Maritime Organization's COLREGS framework and is not subject to unilateral modification by any single state. Iran's publication of charts that conflicted with the TSS was therefore not a formal navigational notice but an implicit threat: vessels using the standard lanes were being told, through a semiofficial channel, that those lanes were now mined or otherwise dangerous. No formal NOTAM or NAVAREA warning was issued through standard IMO channels.

The incident tested whether Iran could functionally replace the IMO-governed TSS with an IRGC-managed corridor system without triggering a formal legal or military response. Tanker operators responded by holding vessels outside the strait on Day 1, validating the IRGC's coercive intent without the need to detain or attack a single ship. The zero-tanker count tracked by Kpler on Ceasefire Day 1 was the direct commercial consequence.