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

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Risk Analysis for Sea Traffic in the Area around Bornholm 34 5.3.2 Effect upon risk (cost-benefit assessment) Combining the accident frequencies from the previous section with the accident consequences yields risk. This study covers a number of different consequences that can be measured in different units, such as number of lives lost, damaged ship hull area, repair time or amount of oil spilt, as described in chapters 3 and 4. All these consequences and units are converted into a monetary measure. If consequences are expressed in monetary units, then risk means expected cost/ expected benefit. The results will be grouped into two classes in order to provide a better overview: • Clean-up costs include all direct costs originating from an oil spill. This concerns spillage from oil tankers as well as from the bunker tanks of ordinary ships • Loss of assets include all other costs concerning the ship owner and crew, such as repair costs, loss of business during repair, total ship loss, loss of cargo and loss of life Results for 2005 traffic data A look at Table 8 shows that crossing collisions account for approx. 60% of all consequences, whereas parallel collisions contribute 30% and groundings 10%. This distribution differs somewhat from the accident frequencies in Table 5. In particular, it appears that groundings have only comparatively small consequences, despite of their relatively high frequency. Table 8 Expected accident costs [DKK] for 2005 traffic data – by accident type Area Parallel collisions Crossing collisions Imprecision groundings Missed-turn groundings Total Bornholmsgat 8,812,000 15,747,000 2,205,000 0 26,764,000 NE of Bornholm 122,000 266,000 303,000 0 692,000 S of Bornholm 200,000 811,000 549,000 0 1,560,000 All 9,135,000 16,823,000 3,057,000 0 29,015,000 Two tendencies are predominant in Table 9, where the results are displayed by consequence type: The highest risk occurs in the Bornholmsgat (where traffic is strongest) and the dominating consequence type is clean-up costs. A combination of both, i.e. clean-up costs in the Bornholmsgat, stands therefore for approx. 75% of all expected costs. These results are equally illustrated in Figure 20 and Figure 22 3 . 3 Note that the figures also include results lying outside the geographical limits of the study area, unlike the information in the tables (see Figure 2 for description of the study area). P:\65775A\3_Pdoc\DOC\P-65775A main report final corr prepared for PDF.DOC .
Risk Analysis for Sea Traffic in the Area around Bornholm 35 As stated in Section 6.3.1, missed-turn groundings do not appear at all in any of the simulations. This is due to the model that was chosen, which is the only scientifically approved model available at the moment. However, it is designed for much narrower straits and therefore does not describe the present situation sufficiently well (discussion in Appendix B). In fact, a number of this type of accident have been observed in the Bornholmsgat. Table 9 Expected accident costs [DKK] for 2005 traffic data – by consequence type Area Loss of life & assets Clean-up costs Total Bornholmsgat 4,916,000 21,848,000 26,764,000 NE of Bornholm 256,000 436,000 692,000 S of Bornholm 641,000 919,000 1,560,000 All 5,812,000 23,203,000 29,015,000 Furthermore, an interesting comparison can be made between consequence types in the Bornholmsgat on one side and the area north-east/south of Bornholm on the other side: The relation between loss of life & assets and clean-up costs is 1:4.5 in the Bornholmsgat, whereas it is 1:1.5 north-east/south of Bornholm. In other words, the contribution of clean-up costs is grossly disproportional only in the Bornholmsgat. Apparently, oil tankers make up a higher share of traffic in the Bornholmsgat than elsewhere, resulting in a larger than average spill per accident. This is little surprising, given that there is more water depth there. Besides, Bornholmsgat is a part of the shortest connection between the Russian oil harbour of Primorsk and the entrance to the Baltic Sea. The risk contribution of small vessels is practically the same as their contribution to accident frequencies. Collisions with fishing boats are responsible for 5.4% or DKK 1.15 million per year, collisions with sailing and motor yachts for 0.6% or DKK 987,000 per year. Results for 2006 traffic data According to the results in Table 10, crossing collisions are responsible for almost 80% of the expected damage. Comparing the weight of expected accident costs (Figure 21 and Figure 23) with that of expected accident frequencies (Figure 15 and Figure 17) shows that parallel collisions have only little effect despite of their high frequency. However, most parallel collisions are of the overtaking collision type, clearly outnumbering the much more hazardous head-on collision type. Collisions with fishing boats contribute 4.0% or DKK 0.99 million per year to the results. For yachts, the contribution amounts to 0.3 % or DKK 105,000 per year. P:\65775A\3_Pdoc\DOC\P-65775A main report final corr prepared for PDF.DOC .
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