J Mar Sci Technol (2007) 12:240–250 DOI 10.1007/s00773-007-0255-8

ORIGINAL ARTICLE

Casualty analysis of large tankers Eleftheria Eliopoulou · Apostolos Papanikolaou

Received: June 1, 2006 / Accepted: June 26, 2007 © JASNAOE 2007

Abstract This article presents detailed results of a comprehensive analysis of recorded accidents of large oil tankers (deadweight greater than 80 000 tonnes) occurring between 1978 and 2003. The analysis encompasses a thorough review of available raw accident data and their postprocessing in a way to produce appropriate statistics useful for the implementation of risk-based assessment methodologies. The processing of the captured data led to the identification of significant qualitative historical trends of tanker accidents and of quantitative characteristics of large tanker accidents, such as overall accident rates per ship-year. Data were also analyzed for all major accident categories separately, taking into account tanker ship size/type, the degree of accident severity, and the oil spill tonne rates per ship-year; this led to the identification of heavily polluted worldwide geographical areas as a result of large tanker accidents. Key words Analysis of tanker accidents · Tanker pollution · Risk assessment

1 Introduction The prime objective of the present study was the identification and quantification of the main hazards that may lead to a tanker’s loss of watertight integrity and may consequently cause environmental damage. Within the framework of EU-funded project Pollution Prevention

and Control (POP&C1), casualty data for the Aframax class of tankers were systematically analyzed and postprocessed as necessary for the application of a risk-based methodology regarding pollution prevention and control resulting from tanker accidents. Further studies beyond those of the POP&C project were conducted independently by the Ship Design Laboratory of the National Technical University of Athens (NTUA), addressing Suezmax, Very Large Crude Carriers (VLCC), and Ultra Large Crude Carriers (ULCC) tankers, and thus practically all classes of large tankers are included in the overall results presented herein. The results show remarkable trends for tanker accidents in the study period (1978–2003) and enable the identification of accident and pollution rates, which are necessary for the implementation of risk-based methodologies in tanker design and operation. Also identified are the heavily polluted worldwide geographical areas as a result of tanker accidents. An effort has been made to link observed trends to historical developments in tanker design and operation (introduction of the double-hull concept), to the age of the tanker fleet at risk, and to the effects of relevant international regulations introduced, particularly the International Convention for the Prevention of Pollution from Ships (MARPOL) and the US Oil Pollution Act OPA90.

2 Approach 2.1 Tanker casualty databases

E. Eliopoulou · A. Papanikolaou (*) National Technical University of Athens, Ship Design Laboratory, 9, Heroon Polytechniou 15 733 Athens-Zografou, Greece e-mail: [email protected]

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Raw accident data are nowadays available from the well-established Lloyd’s Marine Information Services Ltd (LMIS). Much of the accident information con-

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tained in the LMIS database is, however, in textual format. Consequently, it is difficult to extract and analyze this information systematically without further postprocessing. In addition, the LMIS accident categorization is insufficient for the implementation of a rational riskbased methodology, as necessary for the evaluation a ship’s loss of watertight integrity and the ensuing environmental damage, as proposed by the POP&C project (Papanikolaou et al.2). Therefore, a new rational database was first developed to enable the full exploitation of existing accident information for Aframax tankers. The ultimate purpose of this new database was to facilitate the population of the POP&C Risk Contribution Fault Trees (FTs) and Event Trees (ETs) by a team of POP&C experts, considering the main six identified categories of accidents/ hazards, namely collision, contact, grounding, nonaccidental structural failure, fire, and explosion accidents, which can potentially lead to loss of watertight integrity (LOWI) of a tanker’s hull. A detailed description of the POP&C casualty database is presented by Papanikolaou et al.3 Based on the same concept, two additional databases were developed by the Ship Design Laboratory of NTUA, namely one for Suezmax tankers and another containing the largest tanker sizes, namely VLCC and ULCC tankers. These databases were populated according to the POP&C procedure by diploma thesis students of NTUA under the supervision of the authors (Kanellakis4 and Bourikas5). 2.2 Sample of data The analysis presented herein focuses only on accidents that could potentially lead to a ship’s loss of watertight integrity (LOWI). The period of occurrence of accidents studied was 26 years, from 1978 to the end of 2003. The presented studies refer to tankers of the following DWT size segments: — — — —

Aframax tankers: 80 000–119 999 tonnes Suezmax tankers: 120 000–199 999 tonnes VLCC tankers: 200 000–320 000 tonnes ULCC tankers: greater than 320 000 tonnes.

Because the relevant VLCC and ULCC fleet at risk data were available only as the sum of the two categories, the subsequent analysis considers VLCC-ULCC as one common category. Furthermore, only the main subtypes of the above oil tanker categories were considered in the further investigation, namely oil tankers, crude tankers, shuttle tankers, product carriers, and chemical/oil tankers. It is noted that Ore Bulk Oil carriers (OBOs), ore/oilers, and pure

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chemical tankers were excluded from the present analysis because these tanker subtypes have special design/ layout and operational features that are not representative of the whole class of tankers. An overview of analyzed accident records is given in Table 1. 2.3 Fleet at risk information The annual fleet at risk information used in the present analysis is given in Appendix A. The raw data for the Aframax fleet at risk for the studied period and their technical characteristics were provided by Lloyds Register in the framework of the EU-funded POP&C project. These data were further analyzed in order to cure some inconsistencies in the originally disposed fleet at risk data (Papanikolaou et al.6). Suezmax and VLCC-ULCC fleet at risk data were provided to the authors by Intertanko (stemming originally from Clarkson’s database).

3 Accidents potentially leading to LOWI For the six LOWI accident categories identified above, the accident rates per ship-year were calculated by dividing the total yearly number of accidents by the number of ships operational in that year (annual fleet at risk). It is remarkable to note that the yearly frequency of accidents for all studied tanker categories progressively and significantly decreased, particularly in the post-1990 period (Fig. 1). In this graph, the 3-year moving average is also shown to enable a better assessment of the observed trends. Taking into account accidents with serious consequences only, including ship total losses, it appears that Aframax and Suezmax tankers exhibit similar behavior, showing a considerable reduction of accident frequencies in the post-1990 period, whereas the reduction for VLCC-ULCC tankers is less pronounced, but still significant. When considering accidents that caused pollution, regardless of the quantity of oil spilt, it is evident that Table 1. Number of accidents according to tanker size Aframax

Suezmax

VLCC-ULCC

Collision Contact Grounding Fire Explosion Structural failure

232 125 194 79 39 120

135 55 70 48 26 105

150 60 71 81 44 161

Total

789

439

567

VLCC, Very Large Crude Carriers; ULCC, Ultra Large Crude Carriers

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242 Fig. 1. Accident rate per shipyear. VLCC, Very Large Crude Carriers; ULCC, Ultra Large Crude Carriers

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Accident Rate per Shipyear AFRAMAX 3-year average (AFRAMAX) 3 per.moving Mov. Avg. (AFRAMAX)

SUEZMAX 3-year average (SUEZMAX) 3 per.moving Mov. Avg. (SUEZMAX)

VLCC & ULCC 3-year (VLCC ULCC) 3 per.moving Mov. average Avg. (VLCC & &ULCC)

2.00E-01 1.80E-01 1.60E-01 1.40E-01 1.20E-01 1.00E-01 8.00E-02 6.00E-02 4.00E-02 2.00E-02 0.00E+00 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Fig. 2. Navigational accident rate for Aframax tankers with significant regulations shown in boxes. The numbers in the boxes represent the year of adoption of the particular regulation, whereas the position of the boxes in the graph corresponds to the year of implementation of relevant regulations. COLREG, Convention of the International Regulations for Preventing Collisions at Sea; SOLAS, International Convention for the Safety of Life at Sea;

MOU, Memorandum of Understanding; STCW, International Convention on Standards of Training, Certification and Watch Keeping for Seafarers; ARPA, Automatic Radar Plotting Aid; VETTING, measure; OPA90, Oil Pollution Act; GMDSS, Global Maritime Distress and Safety System; ETS, European Telecommunications Standard; ISM, International Safety Management Code; ILO C180, International Labour Organization

the rates of accidents causing pollution also reduced in the studied period, but not to the same extent as for the rate of overall accidents, see Table 2. However, caution is necessary when using these data for future assessments. A related confidence analysis, presented in Appendix B, Table B1, reveals that in some cases, the 95% confidence intervals with respect to the noted average values are quite wide. It should be noted also that a series of IMO regulations concerning the prevention of incidents and accidents has apparently contributed to the observed declining trends of accident rates, particularly in the post-1990 period, marked by the introduction of the Oil Pollution Act OPA 90 in the USA. Figure 2 (Mikelis et al.7) presents the navigational accident rates of Aframax tankers along with some key relevant regulations that could be responsible for the declining trends of particular accident rates. Note that relevant regulations are herein presented according to their year of implementation and it can be expected that their effect

Table 2. Average accident rates per ship-year

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Aframax All accidents Accidents with serious consequences or total losses Accidents leading to pollution Suezmax All accidents Accidents with serious consequences or total losses Accidents leading to pollution VLCC-ULCC All accidents Accidents with serious consequences or total losses Accidents leading to pollution

Pre-1990

Post-1990

1.11E-01 2.27E-02

3.72E-02 7.18E-03

6.45E-03

4.29E-03

9.95E-02 2.19E-02

3.31E-02 8.36E-03

6.43E-03

2.46E-03

6.04E-02 1.37E-02

2.70E-02 8.50E-03

3.99E-03

2.13E-03

should be noticeable with some phase lag, depending on the nature of each regulation. It is also noted that the significant MARPOL 73/78 convention is not indicated on this graph, though it is of importance, as it

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Fig. 3. Navigational accident rates per ship-year

Collision, Accident Rate per Shipyear AFRAMAX

SUEZMAX

VLCC & ULCC

9.00E-02 8.00E-02

OPA 90

7.00E-02 6.00E-02 5.00E-02 4.00E-02 3.00E-02 2.00E-02 1.00E-02 0.00E+00

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Contact, Accident Rate per Shipyear AFRAMAX

SUEZMAX

VLCC & ULCC

4.00E-02

OPA 90

3.50E-02 3.00E-02 2.50E-02 2.00E-02 1.50E-02 1.00E-02 5.00E-03 0.00E+00

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Grounding, Accident Rate per Shipyear AFRAMAX

SUEZMAX

VLCC & ULCC

6.00E-02 5.00E-02

OPA 90

4.00E-02 3.00E-02 2.00E-02 1.00E-02 0.00E+00

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

fell in the pre-1978 period not studied in the present work; the European ERIKA I, II, and III tanker safety packages and the more recent IMO-MEPC-50 provisions regarding the phase out of single-skin tankers are also not shown as they were implemented after 2003. The full version of this particular study on the influence of regulations on the safety record of the AFRAMAX tankers can be found at the POP&C project website (www.pop-c.org). Figures 3 to 5 present the accident frequencies for each accident category separately; a downward trend is observed here as well. The introduction of the US regional agreement OPA 90 is indicated in these figures because it is believed that this particular regulation has had a striking impact on the safety level of tanker designs and consequently has significantly contributed to the reduction of incidents in all accident categories.

3.1 Navigational accident rates Focusing on the navigational accident rates (i.e., collision, grounding, and contact accidents), all tanker sizes exhibit reduced rates in the post-1990 period. VLCCULCC tankers present the lowest rates in the studied period compared to the smaller tanker sizes considered, see Fig. 3. Regulations related to navigational and routing procedures apparently had a positive impact on the reduction of collision and grounding accidents. The International Convention on Standards of Training, Certification and Watch Keeping for Seafarers (STCW), the International Safety Management Code (ISM), and the ILO’s Seafarers’ Hours of Work and the Manning of Ships Convention improved seafarers’ responsibility and crisis management. The VETTING measure introduced voluntarily by the tanker operators has contrib-

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Fig. 4. Fire and explosion accident rates

Fire, Accident Rate per Shipyear AFRAMAX

SUEZMAX

VLCC & ULCC

4.00E-02 3.50E-02 3.00E-02

OPA 90

2.50E-02 2.00E-02 1.50E-02 1.00E-02 5.00E-03 0.00E+00

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Explosion, Accident Rate per Shipyear AFRAMAX

1.40E-02

SUEZMAX

VLCC & ULCC

OPA 90

1.20E-02 1.00E-02 8.00E-03 6.00E-03 4.00E-03 2.00E-03 0.00E+00

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Fig. 5. Nonaccidental structural failure rates

Non-Accidental Structural Failure, Accident Rate per Shipyear AFRAMAX

7.00E-02 6.00E-02

SUEZMAX

VLCC & ULCC

OPA 90

5.00E-02 4.00E-02 3.00E-02 2.00E-02 1.00E-02 0.00E+00

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

uted to increased operational standards and consequently has reduced the rate of accidents of all categories except for nonaccidental structural failures (no enhanced structural surveying was required at that time). 3.2 Fire and explosion accident rates A slight decreasing tendency can be observed in the yearly rates of fire and explosion accidents throughout the studied period, see Fig. 4. Explosion accidents, however, exhibit considerably reduced rates compared to accidents in which fire was the first event. In addition to OPA 90 and the VETTING measure, the ISM Code and requirements regarding sensing devices (SOLAS 2000) apparently had an overall positive impact on the rate of fire and explosion accidents.

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3.3 Nonaccidental structural failure rates The rates of accidents for Suezmax and VLCC-ULCC tankers exhibit a significant peak in the period 1987– 1991, see Fig. 5. Rates for all tanker categories were significantly reduced in the post-1990 period. A separate investigation regarding the relation of nonaccidental structural failures to a ship’s age was conducted (Papanikolaou et al.6) for Aframax tankers. The study showed “bell type” behavior in this relation, whereby a higher frequency of nonaccidental structural failures was observed for middle-aged ships, namely those 11–15 years old, than for more aged ships. Similar trends were found for Suezmax and VLCC-ULCC tankers. This interesting phenomenon might be attributed to a decreased maintenance effort on a ship’s hull structure

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Table 3. Percentage of ships involved in accidents by age Suezmax

VLCC-ULCC

Age

1988

1989

1989

1990

0–5 years 6–10 years 11–15 years 16–20 years >20 years

0 13 67 20 0

0 8 67 25 0

5 5 80 10 0

5 5 61 29 0

Table 4. Percentage of accidents with serious degree of severity including ship total losses Accident category

Aframax

Suezmax

VLCC-ULCC

Collision Contact Grounding Fire Explosion Nonaccidental structural failure

13% 15% 23% 30% 54% 21%

16% 15% 36% 28% 50% 19%

14% 15% 36% 29% 57% 20%

when approaching the assumed design economic life of about 20 years and before the ship changes ownership for an extended economic life with a new operator. In Fig. 5, the relatively high peaks for Suezmax tankers (years: 1988, 1989) and VLCC-ULCCs (years: 1989, 1990) are due to the observed relatively large number of accidents occurring in middle-aged ships, see Table 3. Regulations related to structural inspection and protection, such as Enhanced Survey Program (ESP) surveys and condition assessment programs (CAPs), have had and are expected to have in the future a great impact and to generally decrease the rate of nonaccidental structural failures. 4 Severity of accidents The degree of an accident’s severity is herein defined according to LMIS coding, namely as nonserious, serious, and a ship’s total loss. The LMIS severity coding uses as a criterion a combination of an accident’s consequences in terms of the ship as a platform, of the persons onboard, and of the marine environment. Table 4 presents the percentage of accidents with a serious degree of severity, including ship total losses, for each major accident category. Reviewing these results, the following can be stated: — All three tanker categories considered have similar percentages of accident severity for collision and contact accidents (around 15%). — An increased accident severity percentage is indicated for grounding accidents for Suezmax and VLCC-ULCC (about 36%).

Table 5. Frequencies of accidents with serious degree of severity including ship total losses Accident category

Aframax

Suezmax

VLCC-ULCC

Collision Contact Grounding Fire Explosion Nonaccidental structural failure

2.57E-03 1.63E-03 3.69E-03 1.97E-03 1.72E-03 2.15E-03

3.05E-03 1.16E-03 3.63E-03 1.89E-03 1.89E-03 2.90E-03

1.56E-03 7.04E-04 1.95E-03 1.80E-03 1.88E-03 2.58E-03

— For fire, explosion, and nonaccidental structural failure accidents, all tanker sizes appear to experience almost the same percentage of accidents with high severity. Explosion accidents are inherently related to a high percentage of severity, indicating that if an explosion accident happens, the consequences will be serious, leading even to the ship’s total loss with a high probability (more than 50%). — In summary, explosion accidents are the most severe type of accidents for all studied tanker sizes. For Aframax tankers, fire appears to be the second most severe event, whereas for Suezmax tankers and VLCC-ULCCs, grounding accidents are the second most severe. Table 5 outlines the frequencies of accidents with a serious degree of severity including ship total losses for all major accident categories and tanker sizes. The particular frequencies were calculated by dividing the total number of accidents with a serious degree of severity and ship total losses for the entire studied period by the fleet at risk over the same period. The 95% confidence intervals of these values are given in Appendix B, Table B2. — VLCC-ULCCs exhibit the lowest rates with respect to navigational accidents overall. — For groundings, Aframax and Suezmax tankers present considerably higher severity rates than VLCC-ULCCs. — All tanker sizes experience similar frequencies of highly severe fires, explosions, and nonaccidental structural failures. It is noted, however, that although explosion accidents appear to be related to higher percentages in terms of severe consequences (Table 4), the corresponding frequency rates were not the highest.

5 Spill tonne rates Table 6 presents the oil spill rates in tonnes per ship-year. Aframax tankers experienced higher spill rates in the

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Fig. 6. Spill tonne rates per ship-year. The names of ships involved in major accidents are included in the boxes

Six accident categories, Spilled Tonne Rate per shipyear AFRAMAX 1.00E+03 9.00E+02

INDEPEND ENTA CASTILLO DE BELLVER

8.00E+02 7.00E+02

ATLANTIC EMPRESS

6.00E+02

SUEZMAX ABT SUMMER

VLCC & ULCC HAVER

KHARK 5

IRENES SERENADE

5.00E+02

BRAER

SEA EMPRESS

PRESTIGE

NOVA

4.00E+02 3.00E+02 2.00E+02 1.00E+02

Table 6. Spillage rates (tonnes) per ship-year

2003

2001

2002

2000

1998

1999

1997

1996

Table 7. Spillage rates (tonnes) per ship-year, per category

Tanker size

1978–2003

Pre-1990

Post-1990

Tanker size

Aframax Suezmax VLCC-ULCC

31.16 59.34 114.17

27.52 78.80 143.86

34.81 39.88 84.48

Collision accidents Aframax 2.15 Suezmax 23.59 VLCC-ULCC 25.64 Contact accidents Aframax 0.81 Suezmax 1.69 VLCC-ULCC 0.78 Grounding accidents Aframax 13.07 Suezmax 27.39 VLCC-ULCC 18.74 Fire accidents Aframax 0.06 Suezmax 0.00 VLCC-ULCC 30.77 Explosion accidents Aframax 8.16 Suezmax 2.74 VLCC-ULCC 34.23 Nonaccidental structural failures Aframax 6.92 Suezmax 3.92 VLCC-ULCC 4.01

post-1990 period, whereas Suezmax and VLCC/ULCC tanker ships exhibit significantly lower values in the post-1990 period compared to the period before. These statistics are greatly affected by the possible occurrence of catastrophic accidents; in terms of Aframax tankers, there were two major accidents in the post-1990 period with serious environmental consequences, namely those involving the Braer (amount of spilt oil: 88 214 tonnes in 1993) and the Prestige (amount of spilt oil: 77 000 tonnes in 2002). In Fig. 6, the annual spill rate of each tanker size is presented, along with the most significant accidents that led to environmental pollution of greater than 70 000 tonnes of spilt oil. Further commenting on the pollution rates presented in Table 6, where the six LOWI accident categories have been evaluated, VLCC-ULCC ships clearly exhibit the highest spill rates per ship-year compared to the smaller tanker sizes. This should be expected because these vessels have comparatively large cargo tanks, therefore in the case of loss of the hull’s watertight integrity in the cargo area, potentially a larger amount of oil can outflow. Appendix B, Table B3, presents the 95% confidence intervals of the above spill rates. The calculated intervals are extremely wide and in most cases they numerically approach the average values. This is because of the inherent characteristic of pollution accidents in that there are only a small number of accidents leading to large amounts of pollution. Focusing on each accident category separately, the figures of spill rates vary between the studied tanker sizes, see Table 7:

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1995

1994

1993

1991

1992

1990

1989

1987

1988

1986

1985

1984

1983

1982

1981

1980

1979

1978

0.00E+00

1978–2003

Pre-1990

Post-1990

4.23 27.11 43.62

0.07 20.07 7.66

1.57 3.39 1.18

0.04 0.00 0.38

5.28 34.97 37.25

20.86 19.81 0.24

0.13 0.00 32.42

0.00 0.00 29.12

16.07 5.48 21.40

0.25 0.00 47.06

0.24 7.85 7.99

13.60 0.00 0.02

Collision accidents. Suezmax tankers had similar spill rates in the pre- and post-1990 periods. A significant reduction of rates is seen in the post-1990 period for VLCC-ULCC tankers. Contact accidents. Comparable and significantly lower values of spill rates were seen in the post-1990 period for all tanker sizes. Grounding accidents. Aframax tankers experienced a significant increase of spill rates in the post-1990 period. For the larger ships, reduced rates were evident in the post-1990 period, with the VLCC-ULCC having the lowest values in this period. Fire accidents. Almost zero spill rates for Aframax and Suezmax tankers imply that the majority of fire

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accidents occurred while the vessel was unloaded, as no oil pollution occurred during the accidents. In particular, looking into the details of relevant Aframax and Suezmax accidents, it seems that fire often started in the engine room or the pump room or on the superstructure due to electrical faults or equipment heating. Furthermore, in other cases, the vessel was under repair and the ignition source was from hot works. In contrast, VLCC-ULCC tankers had high rates throughout the studied period. The average of 29.12 tonnes/ship-year post-1990 was accounting for by two accidents. Explosion accidents. Significantly reduced spill rates in the post-1990 period was evident for Aframax and Suezmax tankers, whereas VLCC-ULCC tankers showed a significant increase in this period. The figure of 47.06 tonnes per ship-year in the post-1990 period was accounted for by a single accident. Nonaccidental structural failures. Aframax tankers experienced a significant increase of spill rates in the post1990 period, mainly because of the Prestige incident in 2002. In contrast, Suezmax and VLCC-ULCC tankers showed comparable behavior with negligible spill rates in the post-1990 period. 6 Geography of oil spills Figure 7 shows the worldwide geographic locations of severe oil pollution caused by Aframax, Suezmax, and

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VLCC-ULCC tankers over the period studied (1978– 2003) along with the routes of major worldwide oil movements. Also, in Table 8, the geographic areas with total oil spills per Marsden Grid cell greater than 700 tonnes are identified. The most severely affected areas worldwide (over 100 000 tonnes oil spilt) are: the Caribbean Sea, the Bay of Biscay, Scapa Flow Bay, English Channel, southwest and South Africa, the Bosporus Strait—east Mediterranean, and the Strait of Malacca. A comment is due on the arctic route (northern sea route) statistics, for which no pollution accidents were reported. This is a relatively new but increasingly exploited route driven by the recent large increase of Russian oil exports that also shortens transit distances between other existing and new trade centers. There are several possible reasons for the lack of pollution statistics here: increased navigational caution and support, the hostile environmental conditions, operation by relatively smaller tankers that are not included in the presented large tanker statistics, and possible underreporting for political reasons. 7 Conclusions Accident databases such as the one utilized herein are potentially important tools for assessing the performance of the maritime industry with respect to the safety of tankers and the protection of the maritime environment. They can be used as a rational basis for developments in

Fig. 7. World map of main oil transport routes (EMSA8) and marine pollution as a result of large tanker accidents between 1978 and 2003

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Table 8. Total spill per Marsden grid for areas with pollution greater than 700 tonnes as a result of large tanker accidents from 1978 to 2003 Marsden grid

Number of accidents

Number of accidents involving oil pollution

Total tones spilled (1978–2003)

Geographic area

43 145 371 442 181 180 178 26 142 103 144 109 231 27 82 141 376 432 105 110 441 44 487 116 120 232 132 179 81 131 217 143 216 157

41 28 1 11 36 44 27 113 63 133 5 46 13 6 103 47 14 3 37 6 11 31 1 51 14 2 34 18 18 41 6 45 112 12

4 3 1 1 4 4 3 10 6 3 2 3 4 3 8 3 4 1 3 1 1 2 1 5 4 1 3 3 1 2 3 1 3 1

315 647 285 582 260 000 252 000 196 719 147 017 127 780 100 292 94 722 87 409 82 734 40 570 36 433 25 560 23 729 20 193 18 153 17 983 17 269 11 000 10 161 8 715 5 000 3 785 3 012 2 797 2 166 2 033 1 770 1 337 1 164 1 118 830 770

Aruba Island, Caribbean Sea Bay of Biscay (La Coruna/Brest) St. Helena Island, South Atlantic Ocean Cape Town, South Africa Scapa Flow Bay, UK English Channel Bosporus Strait Strait of Malacca, Singapore Strait, Indian Ocean Mediterranean Sea (Alexandria and Libya) Gulf of Oman (Al Fujairah) Skikda, Algeria Gibraltar British Columbia, Canada Strait of Malacca, Indian Ocean Gulf of Mexico, Corpus Christi/Aransas Bay Suez (Bitter Lake, Port Said) Rio de Janeiro, Brazil Cervantes, Western Australia Jeddah, Suez, Red Sea (Saudi Arabia) 95 Miles NNW of Lisbon Port Elizabeth, South Africa Maracaibo, Venezuela Punta Arenas, Strait of Magellan Delaware Bay, USA Los Angeles, USA Prince William Sound, Alaska Korea Strait (Ulsan, Bussan)—Sea of Japan Mediterranean Sea (Gulf of Venice) Gulf of Mexico (Mississippi, Tampa) Kobe, Japan Sullom Voe Terminal, Shetland Island, North Atlantic Mediterranean Sea (Malta and Sicily Channel) Hamburg Area Strait of Juan de Fuca, North America

the international regulatory process and help to address the weakest links in the tanker safety and environmental protection chain. Additionally, they provide valuable information about the areas of tanker design, maintenance, operation, and crew training that may be in need of additional attention or of a new, risk-based approach. The marine casualty databases that have evolved over the years were not designed with the application of risk assessment methods in mind, and therefore suffer from a number of serious limitations that make their usage in assessment studies problematic. Looking to the future, the increased application of risk assessment methods to ship design, operation, and regulations will lead to an increasing need for good quality, easily available marine casualty data. The methodology and analysis presented in this article might form a valuable basis for the way ahead. The accident rates of large tankers significantly decreased over the period 1978–2003. The rates of accidents leading to pollution as well as the rates of accidents

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with a high degree of severity also reduced, but not to the same extent. Spill rates exhibit a declining trend throughout the studied period for Suezmax and VLCCULCC vessels. Concerning Aframax tankers, a slight increase was found in the post-1990 period mainly because of the Braer and Prestige incidents. A series of regional and international regulatory measures introduced in the past 30 years affecting tanker design, maintenance, operation, and the accelerated renewal of the world tanker fleet has obviously contributed to the improvement of the safety level of tankers and of the safety culture in the tanker shipping industry, as reflected in the present accident statistics. When using results of the present statistical analysis for the forecasting of very serious ship accidents, particularly of accidents with catastrophic impact on the marine environment, one should be cautious. The limited number of such accidents and the complexity of the factors leading to them do not allow firm conclusions about the future, although trends appear optimistic. A confidence analysis

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of the presented statistical data revealed useful uncertainty margins, which are of importance when deciding future regulatory and political measures. The analysis of geographic locations of recorded accidents with high pollution showed that besides the Caribbean Sea, the southwest and south European and southwest and South African coasts were the most heavily polluted by large oil tanker accidents in the period studied. Regarding the pollution of European coastlines, it should be noted that one more casualty with catastrophic environmental consequences, not registered herein because it fell in a smaller DWT tanker category, namely the accident involving the tanker Erika (37 000 DWT) 80 km off Brittany in 1999, led the European Commission to act drastically in the matter by adopting a series of measures known as the ERIKA I and II packages, leading to an accelerated phase out of single-hull tankers operating in European waters (www. ec.europa.eu/transport/maritime/safety/2000_erika_en. htm). Similar measures were subsequently adopted by IMO-MEPC for worldwide tanker operations. It can be expected that these measures will significantly contribute to a decrease in serious large tanker accidents, particularly of those leading to pollution of the marine environment. Acknowledgments. Part of the study presented herein was financially supported by the European Commission under the FP6 Sustainable Surface Transport Programme. The support was given under the STREP scheme, Contract No. TST3-CT-2004-506193. The European Community and the authors shall in no way be liable or responsible for the use of any such knowledge, information, or data, or of the consequences thereof. The authors would like to thank Dr. Nikos Mikelis (IMO, former Intertanko) for fruitful discussions and the provision of data for this study. The authors also thank their final year students Messrs Kanellakis and Bourikas for the initial assessment and processing of part of the raw tanker accident data. Finally, the authors would like to thank the reviewers of this article for their valuable comments and suggestions that increased the value of the presented material.

249 6. Papanikolaou A, Eliopoulou E, Mikelis N (2006) Impact of hull design on tanker pollution. The Ninth International Marine Design Conference, Ann Arbor, Michigan, May 16–19 7. Mikelis N, Delautre S, Eliopoulou E (2005) Tanker safety record at all-time high. Lloyds List, September 29, 2005 8. EMSA (2004) Action plan for oil pollution preparedness and response. European Maritime Safety Agency, Brussels

Appendix A Fleet at risk Year

Aframax total fleet

Suezmax total fleet

VLCC-ULCC total fleet

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Ship-years

372 358 383 412 416 401 382 375 368 380 383 397 414 438 460 463 470 467 481 487 518 552 552 559 568 596 11 652

268 267 263 264 252 247 243 245 235 229 232 236 248 255 268 287 288 283 281 278 288 296 288 292 276 287 6896

709 721 719 692 661 598 539 487 419 402 391 397 412 425 436 440 452 436 431 437 434 430 425 441 428 428 12 790

Appendix B References

Confidence analysis

1. POP&C (2004–2007) Pollution prevention and control. EU project, 6th Framework Programme, www.pop-c.org 2. Papanikolaou A, Eliopoulou E, Mikelis N, et al (2005) Casualty analysis of tankers. RINA Learning from Marine Incidents III, London, January 25–26, 2006 3. Papanikolaou A, Eliopoulou E, Alissafaki A, et al (2005) Critical review of Aframax tanker incidents. The Third International ENSUS Conference, Newcastle upon Tyne, April 13–15, 2005 4. Kanellakis G (2005) Casualty analysis of Suezmax tankers (in Greek). Diploma Thesis, Ship Design Laboratory-NTUA, Athens 5. Bourikas E (2005/2006) Casualty Analysis of VLCC-ULCC tankers (in Greek). Diploma Thesis, Ship Design LaboratoryNTUA, Athens

Due to the nature of the analyzed statistical data, a binomial confidence analysis was considered necessary to establish the uncertainty margins of the obtained averaged values, see Tables B1 and B2. Concerning the spillage rates, the confidence analysis was performed on the basis of mean values, see Table B3. The calculated 95% confidence intervals, presented below, correspond to the 95% probability that certain values will be met. It is observed that in some cases the confidence intervals are quite wide with respect to the average values. In those cases, caution is needed when using the particular values for decision-making purposes.

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Table B1. Average accident rates per ship-year and associated confidence intervals (C.I.)

Aframax All accidents C.I. Lower bound C.I. Upper bound Accidents with serious consequences or total losses C.I. Lower bound C.I. Upper bound Accidents leading to pollution C.I. Lower bound C.I. Upper bound Suezmax All accidents C.I. Lower bound C.I. Upper bound Accidents with serious consequences or total losses C.I. Lower bound C.I. Upper bound Accidents leading to pollution C.I. Lower bound C.I. Upper bound VLCC-ULCC All accidents C.I. Lower bound C.I. Upper bound Accidents with serious consequences or total losses C.I. Lower bound C.I. Upper bound Accidents leading to pollution C.I. Lower bound C.I. Upper bound

Pre-1990

Post-1990

1.11E-01 1.02E-01 1.19E-01 2.27E-02 1.87E-02 2.71E-02 6.45E-03 4.35E-03 8.95E-03

3.72E-02 3.08E-02 3.98E-02 7.18E-03 5.10E-03 9.27E-03 4.29E-03 2.82E-03 6.12E-03

9.95E-02 8.87E-02 1.10E-01 2.19E-02 1.69E-02 2.73E-02 6.43E-03 4.03E-03 9.92E-03

3.31E-02 2.72E-02 3.90E-02 8.36E-03 5.53E-03 1.17E-02 2.46E-03 1.12E-03 4.65E-03

6.04E-02 5.26E-02 6.36E-02 1.37E-02 9.64E-03 1.48E-02 3.99E-03 2.38E-03 5.33E-03

2.70E-02 2.30E-02 3.17E-02 8.50E-03 6.28E-03 1.13E-02 2.13E-03 1.10E-03 3.71E-03

Table B2. Frequencies of accidents with serious or catastrophic consequences and associated confidence intervals Accident category

Aframax

Collision

2.57E-03

Contact

1.63E-03

Grounding

3.69E-03

Fire

1.97E-03

Explosion

1.72E-03

Nonaccidental structural failure

2.15E-03

Suezmax C.I. l.b.: 1.74E-03 C.I. u.b:. 3.67E-03 C.I. l.b.: 9.82E-04 C.I. u.b:. 2.55E-03 C.I. l.b.: 2.82E-03 C.I. u.b:. 5.16E-03 C.I. l.b.: 1.32E-03 C.I. u.b.: 3.06E-03 C.I. l.b.: 1.12E-03 C.I. u.b.: 2.75E-03 C.I. l.b:. 1.39E-03 C.I. u.b:. 3.17E-03

3.05E-03 1.16E-03 3.63E-03 1.89E-03 1.89E-03 2.90E-03

VLCC-ULCC C.I. l.b.: 2.00E-03 C.I. u.b:. 4.83E-03 C.I. l.b.: 5.01E-04 C.I. u.b:. 2.28E-03 C.I. l.b.: 2.35E-03 C.I. u.b:. 5.35E-03 C.I. l.b.: 1.00E-03 C.I. u.b:. 3.22E-03 C.I. l.b.: 1.00E-03 C.I. u.b:. 3.22E-03 C.I. l.b.: 1.77E-03 C.I. u.b:. 4.48E-03

C.I. l.b., confidence interval lower bound; C.I. u.b., confidence interval upper bound

Table B3. Spillage rates in tonnes per ship-year along with the 95% confidence intervals determined for the mean values Tanker size

1978–2003

Pre-1990

Post-1990

Aframax C.I. Suezmax C.I. VLCC-ULCC C.I.

31.16 ± 22 59.34 ± 44 114.17 ± 88

27.52 ± 32 78.80 ± 77 143.86 ± 109

34.81 ± 33 39.88 ± 44 84.48 ± 142

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1.56E-03 7.04E-04 1.95E-03 1.80E-03 1.88E-03 2.58E-03

C.I. l.b.: 1.02E-03 C.I. u.b:. 2.51E-03 C.I. l.b.: 3.22E-04 C.I. u.b:. 1.34E-03 C.I. l.b.: 1.33E-03 C.I. u.b:. 2.98E-03 C.I. l.b.: 1.14E-03 C.I. u.b:. 2.70E-03 C.I. l.b.: 1.27E-03 C.I. u.b:. 2.88E-03 C.I. l.b.: 1.71E-03 C.I. u.b:. 3.53E-03