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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

  1. Ensure bridge watchkeepers receive training on the limitations of AIS and the importance of radar cross-checking in restricted visibility situations (Rec 2020/115).
  2. 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.

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