The incident

On a breezy autumn morning, a ferry had departed harbour and was following a buoyed channel to the open sea.

At the same time, a small cargo vessel inbound towards the channel was preparing to embark a pilot via a ladder on its port side, as had been directed by the VTS (figure 1).

Credit: UK Maib

In order to obtain suitable sea conditions for the transfer, the coxswain of the pilot boat asked the cargo vessel’s master, by VHF radio, to alter course to port, which he agreed to do.

Following there, the pilot boat’s coxswain then informed the ferry’s master of the plan.

The ferry’s master responded by stating his intention to leave the channel passing south of buoys 1 and 2, and that he hoped the cargo vessel would not proceed too far in his direction.

As the cargo vessel started its turn to port, the vessels were just over a mile apart (Figure 2).

Credit: UK Maib

As soon as the pilot arrived on the cargo vessel’s bridge after the transfer, it was immediately apparent that urgent action was required to avoid collision.

In light of the situation, the pilot informed the ferry’s master that he was altering course hard to starboard and, at the same time, the ferry’s master had applied astern power to stop the vessel (Figure 3).

Both these actions prevented collision and, after passing, the vessels continued their passages without further incident.

Lessons learned:

  1. The VTS team has a vital role to play in assisting with collision avoidance. The risk of collision between inbound and outbound vessels in this channel was well documented within the port’s safety management system.
  2. To mitigate this risk the pilot embarkation point (Figure 1) was deliberately positioned east of the channel
    entrance.
  3. The harbourmaster’s guidance to VTS operators was that inbound vessels should not pass the charted embarkation point until the pilot was safely on board. Had the VTS operator followed the harbourmaster’s guidance on this occasion and advised the vessels accordingly, the risk of collision could have been reduced.
  4. A ‘shared mental model’ of a situation can signifcantly aid time-critical decision making. In a VTS area, the ideal outcome is for all vessels and the VTS operator to have a common understanding of a situation, including each vessel’s intentions.
  5. Despite the VHF radio conversations in this case, there was the possibility of misunderstandings between
    the vessels and the VTS operator. This can be mitigated by unambiguous statements of intent and consistent application of local guidance.
  6. Ultimately, the responsibility for avoiding collision rested with the masters of both vessels; in this case the action taken to stop the ferry when an uncertain situation developed was effective in avoiding collision. Equally, the master of the cargo ship could have challenged the request from the pilot boat’s coxswain in order to develop and agree a safer plan.