Why 98.6% of offshore collisions involve authorised vessels — and what to do about it

Most people in the offshore industry have heard the safety-zone collision statistic in passing. Few have sat with it long enough to ask the obvious next question: who, exactly, is doing the colliding?

The answer is uncomfortable, well-documented, and — for anyone trying to build a safer offshore operation — the single most important number on the page.

The number that should change your operating model

UK Health and Safety Executive data published via the Marine Safety Forum recorded 14 dangerous occurrences involving vessel-to-installation contact across a 730-day window — one event roughly every 52 days. Of those events, 98.6% involved authorised attendant vessels: supply boats, ERRVs, walk-to-work vessels, crew transfer craft. Vessels the duty holder explicitly invited inside the 500-metre exclusion zone.

That single fact reframes everything. The safety zone is not failing because the wrong boats are getting in. It is failing because the right boats — the ones we coordinate with, brief, and trust — are colliding with the assets we asked them to support.

Why "more procedures" hasn't fixed it

The traditional response to an authorised-vessel incident is procedural: more checklists, longer briefings, an additional pre-task sign-off. After 20+ years of that response, the rate has not meaningfully moved.

The reason is structural, not procedural. Look at the working model on any given approach:

• The OIM on the installation has one operational picture, derived from radar, VHF and the duty deck officer's verbal report.
• The Master on the attending vessel has a different picture, derived from ECDIS, VHF and what the bridge team can see.
• The shoreside marine coordinator has a third picture, derived from AIS, email and a phone log.

Three pictures, three timelines, one approach. The pictures only fully reconcile when something goes wrong, in the post-incident timeline reconstruction. By then it's already an incident.

The human-factor pattern that actually drives the data

When you read the published narratives of authorised-vessel incidents — and we have read most of them — the same four conditions recur:

1. Asymmetric awareness. One party (typically the vessel) believes a step has been completed; another party (typically the installation) believes it has not.
2. Verbal-only safety stops. A "stand off" is broadcast on VHF and acknowledged. Acknowledgement is not the same as action. Acknowledgement under fatigue, language barrier or radio congestion is even less so.
3. Static, paper-based checklist drift. The checklist on the bridge is version 4. The procedure on the installation is version 7. Nobody noticed.
4. Lost data. The vessel's near-miss, the deferred action, the unusual current — none of it leaves the deck. The next vessel arrives blind to the lesson learned by the last one.

None of these are competence failures. They are coordination failures. They are exactly what happens when you stack three professional teams on three siloed information systems and ask them to perform a safety-critical task together.

The operational fix is synchronisation, not more documents

There is a small but growing body of evidence — and a much larger body of mariner intuition — that the right intervention is not another procedure but a shared operational picture. Specifically:

• A single live visual interface that the OIM, the Master and the shoreside coordinator all read from at the same time.
• Logic-driven digital workflows that physically prevent step-skipping, so "complete" means complete on every screen simultaneously.
• A one-tap, audible "make-safe" broadcast that surfaces on every connected asset's screen at once, rather than relying on a single VHF transmission landing in three different listening environments.
• An immutable, time-stamped digital record of every decision and acknowledgement — not for blame, but so the next vessel and the next campaign inherit the lesson rather than relearning it.

This is exactly the architecture we built GreenHulls SOMS around, because every one of those four conditions above maps to a deliberate design choice in the platform. The point of this article is not to sell the platform — the point is to make the case that the 98.6% number is a coordination problem with a coordination fix, and that the industry has spent two decades treating it as a procedural problem with a procedural fix.

What to do this week, regardless of vendor

Even before any technology change, three things any duty holder can audit immediately:

• Picture symmetry. Pull the radar plot, the ECDIS trace and the marine coordinator's timeline for your last three 500m entries. Are they the same? If not, you have asymmetric awareness right now.
• Acknowledgement vs action. Look at your last safety-stop log. Was the stop verbal-only? Was there any independent confirmation that the requested action — not just the acknowledgement — actually occurred?
• Lesson capture. Where does the supply vessel's bridge log live after the campaign ends? If the answer is "on the vessel" or "in the company's internal system", the next campaign starts from the same baseline as the last one.

The 98.6% number is not destiny. It is the predictable output of an industry-wide operating model. Change the operating model and the number changes with it.

References

• UK Health and Safety Executive, Offshore Dangerous Occurrences statistics (via Marine Safety Forum, 2013–2014 reporting window): 14 vessel-to-installation contact events across 730 days; 98.6% involved authorised vessels.
• Marine Safety Forum, *Safety Alerts and Lessons Learned* archive.
• HSE, *Offshore safety statistics bulletin* (annual).