Contact event tree

Input frequency for cruise ship contact (1.2E-03) is calculated in Section 6. Event tree for contact has been developed and is illustrated in Figure 7-2; further details can be found in Appendix C:

Expected fatalities Contacts Fatalities per accident pr ship year pr ship year

no flooding 0 2.9E-05 0.0E+00

0.5

icebergs remains afloat 5 2.0E-05 1.0E-04

0.05 0.70

flooding slow sinking 100 7.3E-06 7.3E-04

0.5 0.25

40 % fatalities 1600 2.9E-07 4.6E-04 0.2

rapid capsize 80 % fatalities 3200 8.7E-07 2.8E-03

0.05 0.6

100 % fatalities 4000 2.9E-07 1.2E-03 0.2

no flooding 0 2.3E-04 0.0E+00

0.8

offshore structures remains afloat 2 4.1E-05 8.1E-05

0.25 0.7

flooding slow sinking 20 1.5E-05 3.0E-04

0.2 0.26

40 % fatalities 1600 4.6E-07 7.4E-04 0.2

rapid capsize 80 % fatalities 3200 1.4E-06 4.5E-03

0.04 0.6

100 % fatalities 4000 4.6E-07 1.9E-03 0.2

Contact 1.2E-03

no flooding 2 1.0E-04 2.1E-04

bridges 0.9

0.1 remains afloat 2 1.0E-05 2.1E-05

0.9

flooding slow sinking 20 1.0E-06 2.1E-05

0.1 0.09

rapid capsize 800 1.2E-07 9.3E-05

0.01

no flooding 0 6.3E-04 0.0E+00

0.9

harbor structures remains afloat 0 6.3E-05 0.0E+00

0.6 0.9

flooding slow sinking 5 6.3E-06 3.1E-05

0.1 0.09

rapid capsize 300 7.0E-07 2.1E-04

0.01 1.2E-03 1.3E-02

Level 1 Level 2 Level 3 Level 4

Figure 7-2: Contact event tree An explanation to the various branches in the event tree follows suit: Level 1

The serious casualty scenario is further divided into the four possible objects by which the ship can experience contact with. These are icebergs, offshore structures, bridges, and harbour structures. In order to obtain a large enough impact to cause serious casualty the cruise ship must have a certain speed. This is taken into consideration when defining the distribution between the four branches. Icebergs represent a hazard, but the number of cruise ships presently sailing in ice infested waters is limited, yet increasing, and this increases the probability of this scenario (estimated by project participants to 0.05). The offshore structures are increasing in numbers, both as floating and fixed structures, and hence are modelled somewhat higher (estimated at 0.25) than the statistical data (LRFP) suggests. The offshore structures include drifting objects, such as containers and similar. Harbour structures are modelled approximately the same as the statistical number of serious contacts suggests, but somewhat lower (0.6).

Level 2

Contrary to bridges and harbour structures, impacts with offshore structures and icebergs will have an increased probability of penetration below water line resulting in flooding. Since offshore structures are often located in the middle of the sea, the probability for an impact with high speed is larger than for bridge impacts which are usually located where speed restrictions apply. Ice would also hit the cruise ship below water line. The probability figures at Level 3 are derived by the project group.

Level 3

The three scenarios developed from the flooding scenario represent the three typical events often used in similar projects. The Joint North-West European Project for RoPax ships (ref /14/) gives the overall probability of remaining afloat as 84% and rapid capsize as 2%, these numbers are referred to as a benchmark. For this event tree model, the probability of experiencing both slow sinking and rapid capsize for contact with icebergs and offshore structures has been increased compared to the overall numbers from ref /14/. For contact with bridges and harbour structures, the probability has been decreased compared to the overall numbers from ref /14/.

The consequences for sinking and capsizing due to contact with bridge or harbour structures have also been reduced. This takes into account the arguments mentioned above in level 3, along with the fact that the distance from shore is short and thus shore support is more available.

Level 4

The number of fatalities if the vessel sinks rapidly is based on the numbers in Table 7-2 and the discussion there after. To model the risk of collision, the said statistics are used to calibrate the expert judgement of the consequences of a collision followed by water ingress and a rapid capsize.

The information in Table 7-2 is included to provide some useful information on the severity of disastrous events. This information is only used as input to expert judgement on the percentage of fatalities in rapid capsizes.

General comments to assessment of fatalities

Evidently, rapid capsize will lead to a high number of fatalities. The number of fatalities for icebergs and offshore structures are higher than for bridges and harbour structures due to the simple fact that collision with icebergs and offshore structures would occur in cold, open water.

Estimated consequences for 3 selected vessel bands

Ships in Band Number of ships in band Theoretical Fatalities per ship year

Theoretical Number of Fatalities per year in each band Ref 01 (>90,000GRT) 30 0.013 0.4 Ref 02 (60,000-90,000 GRT 53 0.010 0.5 Ref 03 (20,000-60,000 GRT 89 0.008 0.7 Total 172 1.6 Theoretical predicted fatalities per year in current world fleet

Theoretical predicted average number of fatalities per ship year

1.6 0.009

Theoretical predicted average number of ship years per fatality (current fleet)

108.9 CONTACT

Main results from the contact event tree

• The large scale incidents (sinking, flooding and rapid capsize) with an estimated 80% casualty rate drive the results for the contact event tree. This is because the estimated numbers of fatalities is large and the estimated frequencies are not sufficiently low to compensate. Any change in the estimated likelihood or consequence of these large scale incidents will have a direct effect on the

• A return period of 109 ship years per fatality (due to contact).

• 1.6 fatalities (due to contact) per year for the cruise fleet (172 Ships).