94% of Hormuz transits are now outside the IMO lane — what that means for risk assessment

When almost every vessel avoids the formal shipping lane, deviation stops being a red flag. It becomes the baseline. And that creates a serious problem for compliance teams who have built their assessments around it.

Between 1 March and 19 May 2026, Kpler tracked 895 vessel crossings through the Strait of Hormuz. Only 58 of them — 6.4% of total traffic — used the IMO-designated Traffic Separation Scheme route. The remaining 93.6% moved either through the Iranian-defined alternative corridor (53.0%) or via dark or unknown routing patterns with AIS switched off (40.6%).

That single data point forces a fundamental rethink of how the TSS functions as a risk tool in the current environment.

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The TSS was never just a navigation system

The IMO Traffic Separation Scheme through the Strait of Hormuz exists to separate inbound and outbound traffic through one of the world's narrowest and most congested chokepoints. The formal shipping lanes are two nautical miles wide in each direction, separated by a two-mile buffer. Before the crisis, the TSS provided compliance and due diligence teams with a behavioural reference: a vessel following the TSS was doing what was expected. A vessel deviating from it warranted a question.

That reference function has not disappeared. But its meaning has inverted. In the current environment, the TSS is better understood as a benchmark for identifying anomalies within the broader context of disrupted routing — not as the expected norm from which deviations stand out.

The question is no longer "why did this vessel deviate?" when nearly all of them are. The question is what the deviation pattern looks like in combination with everything else known about the vessel.

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Route choice is already stratified by risk profile

Kpler's data on route choice by vessel risk category adds an important layer to this picture.

Among sanctioned vessels, only 2.6% used the IMO route. The majority followed the Iranian-defined alternative corridor or moved through dark and unknown patterns. Among shadow fleet vessels, the IMO route share was only marginally higher at 5.6%. Even among lower-risk commercial traffic — vessels not formally sanctioned and not classified as shadow fleet — only 9.8% used the IMO route.

What this tells risk teams is that route choice alone cannot distinguish between a sanctioned tanker deliberately concealing its movements and a commercially legitimate bulk carrier avoiding Iranian waters for entirely defensible safety reasons. The routing signal is the same. The risk profile is not.

That gap — between a shared observable behaviour and divergent underlying risk — is where the analytical work now has to happen.

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The vessel composition picture

The routing data becomes more significant when set alongside the characteristics of the vessels making up Hormuz traffic.

Of the 622 unique vessels Kpler tracked operating through the Strait between 1 March and 19 May, the risk profile extended well beyond formally sanctioned or shadow fleet categories. More than half — 365 vessels, or 58.7% — were aged 20 years or older. The non-sanctioned, non-shadow category recorded an average vessel age of 19.1 years, approaching the profile seen among sanctioned vessels (22.2 years average) and shadow fleet vessels (24.3 years).

The insurance and classification picture is similarly concentrated. In that 622-vessel sample:

• 55.5% operated outside International Group P&I cover — the thirteen mutuals that insure around 90% of global ocean-going tonnage and provide the high-limit third-party coverage most charterers and banks require
• 48.1% operated without IACS classification
• 27.3% had no identifiable ISM manager information

This is not primarily a sanctioned fleet story. These characteristics appear across the wider transit population. The finding is that as total transit volumes declined sharply from crisis levels, the vessels continuing to operate through the corridor are disproportionately those with weaker operational transparency, insurance coverage and classification profiles.