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Stopped or Moving? The AIS Misread That Caused a Gibraltar Collision

🕑 5 min read words Safety • Incident • Navigation

Vessel: ANL Wyong (container ship) and King Arthur (general cargo vessel)
Date & location: 4 August 2018, approximately 4nm SE of Europa Point, Strait of Gibraltar
Outcome: Collision in fog — no injuries; both vessels sustained damage after an AIS misread and a VHF call at the critical moment removed the window for avoiding action
Human factors: Situational Awareness · Communication · Normalisation
Source: MAIB Report 7/2020

~2 min between the VHF call and the collision0 injuries~6 min read + Knowledge Checker

Stopped, or Making Way?

On 4 August 2018, the container ship ANL Wyong and the general cargo vessel King Arthur were both navigating in fog approximately 4 nautical miles south-east of Europa Point, in the Strait of Gibraltar. ANL Wyong was making way, her AIS transmitting speed and heading. The OOW on King Arthur misread ANL Wyong's AIS data, concluding incorrectly that the vessel was stopped.

Two Minutes on the Radio

Based on that incorrect assessment, no collision avoidance action was initiated. Then, approximately two minutes before the collision, a VHF radio call came in. The OOW engaged with it at exactly the moment collision avoidance action was most needed. The two vessels collided; both sustained damage. No one was injured.

What AIS Can't Tell You

MAIB's investigation found over-reliance on AIS for collision avoidance, without radar cross-checking, as the underlying cause — AIS speed-over-ground data was misinterpreted, and nothing forced a second check against the radar picture before a decision was made. Fog demands heightened watchkeeping standards. In the Strait of Gibraltar, one of the busiest shipping lanes in the world, that standard wasn't met at the critical moment.

Recommended Actions

Ensure bridge watchkeepers receive training on the limitations of AIS and the importance of radar cross-checking in restricted visibility situations (Rec 2020/115).
Implement bridge procedures for managing VHF communications during close-quarters situations, including designation of a second officer to handle radio when the OOW is engaged in collision avoidance (Rec 2020/116).

Human Element Analysis

Situational Awareness

AIS speed-over-ground data was misread as showing ANL Wyong stopped, when she was in fact making way. That single misinterpretation removed the trigger for any avoiding action to begin.

Communication

A VHF call arriving during a developing close-quarters situation competed directly with collision avoidance for the OOW's attention — and won, at the exact moment the window for action was closing.

Normalisation

AIS has become, on many bridges, the primary tool watchkeepers reach for first in restricted visibility. Radar remains the ground truth for close-quarters decisions, but MAIB found it wasn't used as the cross-check it's meant to be here.

How This Pattern Repeats

Industry	Incident	The parallel
Aviation	Überlingen mid-air collision, 2002	Over-reliance on one system's guidance (TCAS) over a controller's instruction, combined with communication confusion at the critical moment, led directly to a fatal mid-air collision — the same over-reliance on a single data source, and the same critical-moment communication distraction, MAIB found in the Wyong/King Arthur collision.
Rail	Ladbroke Grove rail crash, 1999	A signal was passed at danger in circumstances involving restricted visibility and a misread of the available information, leading to a fatal collision — the same combination of restricted visibility and a misinterpreted signal that preceded the Gibraltar collision.
Nuclear	Three Mile Island, 1979	Operators misread available instrumentation and took action, or failed to act, based on an incorrect picture of the plant's actual state — directly analogous to King Arthur's OOW acting on a misread AIS picture rather than the ground truth radar was there to confirm.

See How You'd Handle It

The scenario opens on King Arthur's bridge in fog, AIS showing a target ahead, as the VHF crackles to life. Play the ANL Wyong decision scenario and find out where each choice actually leads.

Lessons for Bridge Watchkeepers

AIS data must always be cross-checked against radar in fog and restricted visibility — it's a supplementary tool, not a primary collision avoidance solution.
A VHF call during a developing close-quarters situation should be deferred or handed to a second officer — communication tasks compete directly with collision avoidance for attention.
Actively verify AIS speed-over-ground data rather than assuming a vessel's motion state from a single glance at one parameter.
In high-traffic, restricted-visibility areas, have a defined procedure in place beforehand for managing competing demands on the OOW's attention — don't work it out in the moment.

Test Your Knowledge

Think you've got this covered? Put it to the test in Crew Connect's free Knowledge Checker — try a quick colregs round and see how you score.