Collision in Known Traffic Black Spot
The Danish Maritime Accident Investigation Board has released its report into the collision between the tanker Kraslava and cargo ship Atlantic Lady citing a known traffic blackspot in the waters of Denmark.
On November 1, 2014, the Marshall Islands-registered chemical/products tanker Kraslava collided with the St. Kitts & Nevis-registered refrigerated cargo ship Atlantic Lady in the Drogden Channel, Denmark. The vessels were travelling through dense fog.
The bridge team on each ships was aware of the other ship’s presence in the channel, but both misjudged their own and the other ship’s position. When the actual situation was acknowledged on both ships, it was too late to maneuver to avoid the collision.
Both ships anticipated to have the closest point of approach at the southern exit/entrance to the channel, which was 300 meters wide and where there was little or no visibility. During the approach to buoys no. 17 and no. 16, both ships assumed that the other ship would position itself in the outermost part of the channel. At the time of the collision, the bridge teams on both ships were convinced that the other ship was on the wrong side of the channel and that their own ship was in the outer perimeter; when in fact, both ships were approximately in the middle of the channel.
The investigators concluded that the collision happened as several coinciding factors were present within a narrow geographical area and occurred within a very short span of time. This reduced the margin for failure to an extent that was not recognized by either of the bridge teams.
The factors included restricted visibility, navigating in a narrow channel, the north-easterly current, a pilot boat being alongside Kraslava, and Atlantic Lady making a large course alteration. Individually these factors did not constitute a recognizable significant risk, but in conjunction they created a small margin between success and failure; a safety margin that was based on whether the ships were positioned 50-100 meters to each side of the channel.
Passing at small distances is usually not problematic in channels when the ships are on opposite courses, but in this instance, when both ships were impaired by restricted visibility and one of the ships was to make large course alterations, then the situation became unstable, because they could not rely on instrumentation alone due to the ships’ close proximity to each other.
The factor instrumental in the collision was thus that Atlantic Lady’s approach to the Drogden Channel, in the absence of other better alternatives, necessitated a large turning maneuver. Due to the north-easterly current and the restricted visibility, which delayed the start of the turn until buoy no. 16 was abeam, the turning maneuver brought the ship into the center of the channel, where it crossed ahead of Kraslava.
An analysis of navigation in the southern approach to the Drogden Channel made in 2009 by the Danish Maritime Safety Administration showed that the area was difficult to navigate in and recommended initiatives to improve the flow of traffic in the area; primarily for avoiding groundings and allisions with the buoys. This accident shows that risk of collisions can also be mitigated by these initiatives, state the investigators.
The report is available here.