WATCHOUT - Erroneous AIS data led to a two-ship collision in poor visibility
In this series, we take a look at maritime accident reports and the lessons that can be learned
What happened?
A containership and a gas carrier collided in dense fog, causing damage to both ships, but no injuries or pollution. The collision occurred in the early hours of the morning in a busy shipping area. The containership had come to a complete halt after receiving instructions to do so by local Pilots. The gas carrier was travelling forward, making its way towards a transfer position nearby.
The gas carrier’s Master altered course to starboard, intending to pass the other vessel astern. Although he could not visibly see the containership, he used AIS data to inform his assessment of the situation. Unfortunately, he did not realise that the containership was not moving, as this was not detectable by the AIS. The Master’s course change put his own vessel in direct line to collide with the other ship, which it did shortly after the alteration was made. Corrective action of applying full starboard rudder was attempted, however this happened too late to prevent the collision from happening.
Why did it happen?
- Despite the poor visibility and high levels of traffic in the area, the gas carrier’s Master solely used AIS data to inform his course alterations. This was in spite of the official requirement to only use AIS to support safe navigation in strict compliance with the COLREGS. The Master’s decisions about collision avoidance should have been based primarily on systematic visual and/or radar observations, not just on AIS.
- The AIS data received from the stationary vessel did not include sufficient information to reveal to the gas carrier that it was not moving forward. This caused the Master to input the wrong course alteration, as he believed the other ship to be in motion. Whenever a shipping situation requires analysis to determine the risk of collision, radar target and ARPA data should be used in preference to the received AIS information.
- Neither bridge team fully appreciated the risk of collision in sufficient time to take any meaningful action to avoid the incident. In addition, neither vessel received a collision warning from anyone ashore, despite the location being a designated vessel traffic service area.
- VHF radio conversations were taking place on the gas carrier at the time, proving a significant distraction to those on the bridge while the situation was unfolding.
What changes have been made?
- Both vessels have carried out internal audits and safety reviews following the collision and taken steps to prevent a recurrence.
- Both vessels have issued articles and circulars about the issues raised to their wider fleet, including safety requirements for navigating in restricted visibility.
- Additional training in the use of AIS and other collision avoidance techniques has been provided to bridge members involved in the incident.