Risk Analysis of Sea Traffic in the Area around Bornholm, 2008. - VTT

Risk Analysis for Sea Traffic in the Area around Bornholm
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3 Limits of the Analysis
3.1 Scope
3.1.1 Accidents
The scope is limited to those types of ship accidents that are directly dependent
on the local situation and that can be expected to be affected by a change in the
sea route system. This is typically the case for collisions and groundings, while
not being the case for fires on board, system failure and similar events.
Parallel collisions
Crossing collisions
Powered groundings
Drift groundings
Accidents involving
small vessels
This collision type concerns all ships that are sailing on a parallel or almost
parallel course, as it can be observed along sea routes. There are two types of
parallel collisions, i.e. head-on and overtaking collisions.
All other collisions between two moving vessels are classified as crossing
collisions.
If a ship runs aground or ashore despite of fully operational propulsion and
rudder systems, the event is referred to as powered grounding. The study differentiates
between two types of powered groundings: Those that are due to
imprecise navigation and those that occur if bridge personnel are unable to follow
their duty over a prolonged period, leading to a head-on collision with a
ground or coast. This second grounding type is typically due to alcohol, sleep,
sudden disease or various distractions. A failure of information systems may
equally have an effect here.
This grounding type occurs due to wind and wave action after system failure on
board of the vessel. It is critical mostly in very narrow navigational channels,
such as Øresund, where a ship drifts aground after a comparatively short time.
This cannot be compared to the area around Bornholm, where there is much
more space. Drift groundings are therefore not investigated in the study.
The above models are based on traffic data obtained through the Automatic
Identification System (AIS). Only ships with 300 gross tons and more are
obliged to use AIS devices, although some minor ships also do. Available data
is therefore much more limited for small vessels, which mainly include fishing
boats and yachts (see traffic data description in chapter 4.2).
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