Designing for safety in passenger ships utilizing advanced evacuation analyses—A risk based approach

Safety Science 44 (2006) 111–135 www.elsevier.com/locate/ssci

Designing for safety in passenger ships utilizing advanced evacuation analyses—A risk based approach Erik Vanem *, Rolf Skjong DNV Research, Det Norske Veritas, Veritasveien 1, 1322 Høvik, Norway Received 15 February 2005; received in revised form 27 May 2005; accepted 24 June 2005

Abstract This paper describes a novel set of well-defined evacuation scenarios for use in advanced evacuation analyses of passenger ships according to present maritime safety regulations. The scenarios are based on a recently performed risk assessment of passenger ship evacuation and can be related to actual accident scenarios, covering the major hazards passenger ships are exposed to. Furthermore, a risk-based methodology for using the set of scenarios in evacuation performance evaluation is proposed and it is demonstrated how the scenarios can be used to relate actual design options to the overall level of risk associated with the ship. The paper includes a brief introduction and describes the background for developing the evacuation scenarios. The results from a recently performed risk assessment is reviewed and it is explained how this can be used as basis for deriving a complete set of realistic evacuation scenarios. Furthermore, it is outlined how to use the evacuation scenarios to estimate the overall risk associated with a specific passenger ship. Finally, possible future developments of the maritime safety regulations have been discussed and it has been demonstrated how the proposed set of scenarios will facilitate the emergence of truly risk based probabilistic safety regulations.
2005 Elsevier Ltd. All rights reserved. Keywords: Passenger ship safety; Risk management; Evacuation analysis; Risk-based design; Maritime safety; Safety regulations

*

Corresponding author. Tel.: +47 67 57 70 09; fax: +47 67 57 75 20. E-mail addresses: [email protected] (E. Vanem), [email protected] (R. Skjong).

0925-7535/$ - see front matter
2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssci.2005.06.007

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1. Introduction Recent development of passenger ships has lead to larger and larger vessels with an increasing capacity for carrying people. Modern cruise liners have the capacity of carrying several thousand people on board and even though accidents involving such large passenger ships are rare, if a serious accident should occur, its consequences could be disastrous. The safety of large passenger ships is thus an increasingly important issue. Some previous catastrophes involving a large number of fatalities on passenger ships are the collision of the Admiral Nakhimov in 1986 (425 fatalities), the capsizing of the Herald of Free Enterprise in 1987 (193 fatalities), the collision and subsequent fire and sinking of the Dona Paz in 1987 (4386 fatalities), the fire on the Scandinavia Star in 1990 (158 fatalities), the foundering of the Estonia in 1994 (852 fatalities) and the fire and subsequent sinking of the Dashun in 1999 (282 fatalities). These are just some examples of major accidents involving passenger ships, and although all the accidents are characterized by a set of very particular circumstances that lead to the catastrophe, they serve as good examples of the grave consequences that might result from passenger ship accidents. In an attempt to improve the passenger and crew safety, current IMO regulations for ro-ro passenger ships require that escape routes shall be evaluated by an evacuation analysis early in the design process (IMO, 2001a) in order to prove that the evacuation arrangements are adequate. Interim guidelines for such evacuation analysis are approved by the Maritime Safety Committee (MSC) (IMO, 2002), outlining two distinct methods for evacuation analysis, i.e. a simplified evacuation analysis or an advanced evacuation analysis. Recently, much attention has been paid to the development of sophisticated evacuation models for advanced analyses of evacuation from passenger ships (Lee et al., 2003). However, less effort has been directed towards including such evacuation models in a holistic framework for risk assessment, although evaluation of design and escape arrangements of passenger ships in such a structured way would be completely in line with current developments towards risk based approaches in maritime regulations. The evacuation scenarios presented in this paper facilitate use of advanced evacuation models within a risk based framework, and the methodology for doing this will be further outlined in this paper. If simulations of evacuation from passenger ships are to be meaningful, a set of clearly defined evacuation scenarios are required, and these scenarios should not be modified when comparing alternative design solutions. In order to gain meaningful information from the evacuation simulations, the scenarios also need to be as realistic and relevant as possible. Furthermore, the scenarios should be developed with and anchored in a basic understanding of the overall risk, thus this paper outlines and proposes a novel set of welldefined evacuation scenarios that will enable truly risk-based evacuation analyses. There are a number of different factors that make up an evacuation scenario and these should all be clearly defined in such a way that they unambiguously describe the scenario. The different factors may relate to the total number of people on board, the demographics of the population on board the ship, the type of accident the ship is exposed to, the time of day when the mustering alarm sounds, the weather condition at the time of accident (influencing the movement of the vessel), the lack of accessibility of different parts of the ship (e.g. due to an accident) etc.

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Two parameters determine the risk associated with evacuation situations, i.e. the probability of such a situation to occur and the expected consequence of the incident. The evacuation simulations will provide an estimate of the consequence related to a specific situation, i.e. the results from the simulation will indicate the expected number of fatalities for a given scenario. In order to estimate the risk however, one also need to know the probability of that particular scenario occuring. The total risk associated with evacuation from a specific ship will then be the sum of the risks associated with all relevant scenarios: RISKEvacuation ¼ RISKScenario 1 þ RISKScenario 2 þ


þ RISKScenario N

ð1Þ

This is a function of the probabilities and the consequences of the different scenarios, the latter being estimated from the outcome of the evacuation simulation of the scenario in question. That is, with P(Sc x) denoting the probability of Scenario x and SimRes(Sc x) denoting the simulated consequence of that scenario in terms of number of fatalities, Eq. (1) takes the following form: RISKEvacuation ¼ PðSc 1Þ  SimResðSc 1Þ þ PðSc 2Þ  SimResðSc 2Þ þ


þ PðSc NÞ  SimResðSc NÞ

ð2Þ

If a well defined set of evacuation scenarios covering the major hazards were available and associated with probabilities of occurrence, the above risk could easily be estimated utilizing maritime evacuation simulation software such as the one developed within the FIRE EXIT project, maritimeEXODUS (FIRE EXIT; Galea et al., 2004). Simulations of the different scenarios could be executed for various design alternatives and the optimal solution regarding passenger safety in evacuation situations could be identified, i.e. the design with the lowest associated risk. The aim of this paper is to propose a set of well defined scenarios that can be used when performing evacuation simulations for passenger ships. Each scenario will be associated with a probability of this scenario to take place, based on a thorough risk assessment of evacuation from passenger ships. Another goal is that this set of evacuation scenarios should be as complete as possible in order to give an accurate estimate of the total risk associated with evacuations from passenger ships. Accident scenarios will be grouped into a few types of evacuation scenarios so that one simulation scenario can account for one or more actual real-life scenarios. For example, different types of accidents that have the same effect on an evacuation process can be grouped together as one scenario as far as the simulations are concerned. The probability associated with this simulation scenario should then be the sum of the probabilities of the different accident scenarios it describes. In this paper, the rationale for developing meaningful and risk-based evacuation scenarios will be outlined and a complete set of such scenarios will be suggested. Furthermore, it will be suggested how such risk-based evacuation analyses can be utilized within safety regulations. 2. Background Results from two main sources will be used as background information for developing the risk-based evacuation scenarios. First, a few benchmark scenarios adopted by the MSC for use in advanced evacuation analyses will be used as a starting point (IMO,

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2002). Secondly, a survey of historic accidents involving passenger ships has been performed that provides useful information about accident frequencies and expected available evacuation times (Vanem and Skjong, 2004a,b). Together, these two sources of information provide sufficient data to be used as a foundation to develop more realistic evacuation scenarios. All the different parameters defining a scenario to be used in evacuation simulations can be grouped into four categories in order to facilitate their use, namely geometrical, population, environmental and procedural. The geometrical category includes the layout of escape routes, their obstruction and partial unavailability and initial passenger and crew distribution. The layout of escape routes will vary for different ships and for different designs of a specific ship. This is normally the parameter one wants to test and it will thus represent variable inputs to the simulations. The possible obstruction and partial unavailability of certain parts of the escape routes can be a result of an accident. When generating simulation scenarios, one should therefore try to map different types of accidents into such quantitative effects on the evacuation process, and this is one of the purposes of the current study. Reasonable initial distribution of passengers and crew will be an important part of the scenarios, and a couple of different proposals have been made by MSC, as described in Section 2.1. The population category is the different parameters related to the persons on board and the population demographics, i.e. parameters such as distribution of age, gender, physical conditions (e.g. disabilities), response time, family or group bindings etc. It will be important to map these parameters into qualitative effects on the evacuation simulations such as walking speed under different conditions etc. These issues have received some attention (e.g. UK, 2004; Yoshida et al., 2001; Gwynne et al., 1999) and have been considered within the FIRE EXIT project (Caldeira-Saraiva et al., 2004), but are considered out of scope of the present study. The MSC has also proposed a composition of the population that are to be used for all scenarios for ships with unrestricted operations, and this can be used as a default distribution. For the purpose of this study, it is sufficient to assume a reasonable and realistic population of the ship exist. The environmental category describes static and dynamic conditions of the ship, e.g. caused by the weather conditions or list caused by an accident. Any spread of fire, smoke and toxic gas in a scenario should also be included in this category and such effects should be identified for different accidents and included in the scenario definition. The last category of parameters is the procedural category. This covers the procedures for the crew members ready to assist in an emergency, as well as procedures for passenger responses. For example, should they collect life jackets in their cabins before heading for the muster station or should they proceed to the muster station immediately when the muster alarm sounds and receive their life vests there? An evacuation simulation in this context can be utilized to evaluate such procedural parameters. For the purpose of developing scenarios in the current study, no specific models for crew procedures are considered. Excluding the population and procedural parameters from the scope of the current study (assuming appropriate default values exist), one is left with the geometrical and environmental categories of parameters that define the different evacuation scenarios. These categories can be further decomposed as illustrated in Fig. 1 and specifically, three factors are to be determined from the accident scenarios: Possible obstructions or unavailability of some parts of the ship, dynamic and static conditions of the ship due to weather and sea

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Geometrical parameters

Initial distribution

Obstructions

115

Environmental parameters

Ship motion

Fire/Smoke

Determined by the accident scenarios.

Fig. 1. Parameters defining the evacuation scenarios.

state or accidents and the possible presence of fire and/or smoke. Reasonable parameterisation of these factors, coupled with reasonable initial distribution of people define the evacuation scenarios for use in the simulations. It should be noted that a distinction between accident scenarios and evacuation scenarios will be made in this study. An accident scenario is a scenario that describes a certain generic accident type, e.g. fire, collision or grounding, while an evacuation scenario is a scenario that is to be utilized by the evacuation simulators. An evacuation scenario will thus be parameterised from accident scenarios by its effect on the evacuation performance and one evacuation scenario can correspond to one or more accident scenarios. Each accident scenario will be associated with a corresponding probability, and these probabilities will be used to aggregate probabilities related to the different evacuation scenarios. 2.1. MSC benchmark scenarios In the interim guidelines for evacuation analyses (IMO, 2002), four typical benchmark scenarios and relevant data are specified for use in evacuation simulations. Furthermore it is requested that these four scenarios should be considered as a minimum for the required evacuation analyses. They are derived from the FSS Code (IMO, 2001c) (chapter 13) and describe the initial distribution of passengers in two different cases; night case and day case. • Night case: Passengers in cabins with maximum berthing capacity fully occupied, 2/3 of the crew members in their cabins and the remaining 1/3 of the crew with the following distribution: 50% initially located in service spaces behaving like passengers,1 25% located at their emergency stations and 25% initially located at assembly stations and proceeding towards passenger cabins in counterflow with evacuees. Once the passenger cabins are reached, these crew members will move back to the assembly stations.

1

That is having walking speed and reaction times as specified for passengers.

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• Day case: Passengers in public spaces occupied to 3/4 of maximum capacity. As for the crew, 25% should be located at their emergency stations and 25% should be initially located at the assembly stations, proceeding towards passenger cabins in counterflow with evacuees. Once there, they will return to the assembly stations. The remaining 50% of the crew will behave as passengers1 and have the following initial distribution: 1/3 in public spaces, 1/3 in service spaces and 1/3 in accommodation spaces. In addition to the different initial distribution of passengers and crew, the day and night case also differ in other characteristics such as the response times of the passengers. For the night case, the response times of the population will be doubled compared to the day case. For both the day and night initial distribution of passengers and crew, two different evacuation scenarios that differ in the availability of the escape routes are suggested, resulting in four different scenarios. These are: 1. Primary night evacuation case: Equivalent with the night case above with no further restrictions, i.e. full availability of all escape routes. 2. Primary day evacuation case: Equivalent with the day case above with no further restrictions, i.e. full availability of all escape routes. 3. Secondary night evacuation case: The same population demographics as the night case above, but only considering the main vertical zone associated with the longest assembly time and with one of the two alternative additional restrictions described below. 4. Secondary day evacuation case: The same population demographics as the day case above, but only considering the main vertical zone associated with the longest assembly time and with one of the two alternative additional restrictions described below. Additional restrictions to the secondary evacuation cases: • Alternative 1: Only 50% of the stairway capacity within the identified main vertical zone is available for the simulation. • Alternative 2: 50% of the persons occupying one of the main vertical zones neighbouring the identified main vertical zone are forced to move into the zone and proceed to the relevant assembly station.

2.2. Results from recent risk assessment A survey of passenger ship accidents occurring between (and including) the years 1990 and 2002 has recently been carried out (Vanem and Skjong, 2004a,b). In this survey, the three main causes for an evacuation from passenger ships, namely fire, collision and grounding, were studied. The investigation revealed the frequencies with which the different types of accidents occurred as well as the requirements on maximum evacuation times imposed by the different accident types. The estimates were derived based on a combination of different techniques, e.g. investigating historic accident data for the frequencies of initial events, attained subdivision index for survivabilities and the Delphi technique for the expected consequences. Even though evacuation from passenger ships is normally thought of as most relevant in connection with fires on board, and the current requirements regarding evacuation

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Probability of time available for evacuation > T. P(T)

times from passenger ships corresponds to the requirements related to confinement of fires within each main fire zone (IMO, 2001a), the recent survey suggests that collision and grounding are even more critical regarding evacuation from passenger ships. This is due to the fact that these types of accidents generally leave less time for evacuation than fire accidents. If a ship should sink subsequent to a collision or a grounding accident, it will obviously impose an absolute maximum time for evacuation—the time it will take the ship to sink or capsize, rendering evacuation no longer possible. In a typical fire accident, it will be more crucial to rapidly evacuate certain affected fire zones than to rapidly abandon the whole ship. Only rarely will a fire result in damages that are extensive enough to cause the ship to sink, and fires that do escalate will normally be delayed by firewalls separating the fire zones. Furthermore, those ships that sink due to a fire will normally start sinking after a certain period of time, typically in the order of days. People on board that are not directly exposed to the fire will thus generally have enough time to abandon the ship before the fire spreads throughout the ship. For those people occupying the areas of the fire (within the same fire zone), however, there may be very little time available to escape before heat and toxic gas becomes a major threat towards life and health. The graph in Fig. 2 displays the expected available evacuation times for the different accident types, as found in the risk assessment, and it clearly indicates that collision and grounding cause more critical evacuations than fire. The assessment also concluded that the probabilities of emergency evacuations due to the different types of accidents are comparable whereas the total risk is completely dominated by the collision scenario. When establishing simulation scenarios, therefore, one should include scenarios corresponding to collision and grounding accidents as well as fire. Table 1 displays the probabilities of emergency evacuations due to the different types of accidents as well as the potential loss of lives (PLL) for a generic ship with 3000 people on board. All estimates are per shipyear.

1

B

0.8

A

0.6

E D

0.4

C

0.2 0 0

15

30

45

60

75

Time T (min)

Fire - Passenger ships (A) Fire - Cruise liners (B) Collision (C) Grounding - capsizing (D) Grounding - gracefully sinking (E) Fig. 2. Expected available evacuation times.

90

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Table 1 Probabilities of emergency evacuation Type of scenario

Probability of emergency evacuation

Fire–ro-ro passenger ship Fire–cruise liner Grounding Collision

4.4 · 104 2.6 · 103 1.1 · 104 6.9 · 104

PLL (N = 3000) 1.4 · 102 1.5 · 101 1.3

2.3. Advanced evacuation simulators The recent interest in evacuation simulation software has been considerable (e.g. Lee et al., 2003) and has resulted in a number of different software packages that can simulate an evacuation process onboard a passenger ship. Examples of such simulators are the AENEAS software from Germanisher Lloyd and TraffGo GmbH (AENEAS), EVAC software from Safetec (EVAC), the Evi software from Safety at Sea Ltd. (EVI) and the maritimeEXODUS software package developed in cooperation with the Fire Exit project at the University of Greenwich (EXODUS). The alternative software packages utilize different methods for the calculations within the simulations and naturally include different features and characteristics. In general, the evacuation scenarios defined in this report will be generic and compatible for use with any evacuation simulation software regardless of its functionality. It should therefore not be strictly necessary to know the characteristics and capabilities of any specific software prior to developing the scenarios. However, when it comes to modelling of such effects as spread of fire and smoke and trim and heel,2 the capabilities of the software will determine whether the scenarios can be applied directly or if such effects need to be further defined. For evacuation software that are not able to model trim and heel for example, such effects could be accounted for by adding safety factors to the simulation results. Even though the scenarios developed in this study are not linked to any specific software, the maritimeEXODUS package will be used as an example of the capabilities of such software. The maritimeEXODUS software models the evacuation process within a specific vessel layout by modelling the individual evacuees. Each person on board is individually labelled and given an initial position on board the ship, a response time, age, gender etc. These parameters are randomly drawn from a distribution function and determine the capabilities of that person, e.g. age and gender influence the maximum walking speed. When the evacuation simulation is executed, each evacuee will proceed towards its individual goal, e.g. a specific muster station or life boat, by individual movement based on individual probabilistic decisions. The output from a simulation provides information such as number of people successfully escaped as a function of time, the number of fatalities as a function of time, etc. It will also be possible to track down individual evacuees, and for each person it is possible to view the path that was taken during the evacuation. It is also possible to view the location where fatalities occurred and the starting position of the fatalities. Other options are to

2 Trim and heel are maritime expressions related to the angular movement of a vessel in the longitudinal and the transverse plane respectively.

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Fig. 3. Display of fire spread in maritimeEXODUS.

view the population density of the different part of the ship or the footfall where one can identify the most frequently used escape routes. Features in the maritimeEXODUS allow modelling directly the impacts of some of the accident scenarios. For example a fire hazard can be specified and the software can model and display how temperatures and smoke will spread within the vesselÕs layout because of the fire. The effect on the evacuees can be modelled, e.g. high concentration of smoke might force the evacuees to crawl and stagger and even suffocate if the concentration is high enough. Fig. 3 shows how the spread of fire is modelled and displayed with the maritimeEXODUS.3 Another option is to display the spread of smoke instead of the temperature. Another possible impact from some of the accident scenarios is the development of trim or heel and the dynamic motion of the vessel. This effect can also be accounted for with advanced maritime evacuation simulation software, and the impact of the evacuee behaviour is modelled in variations in the walking speed with the presence of trim and heel. Fig. 4 shows how the heel and trim information is displayed in the maritimeEXODUS.3 Other scenario-related effects such as night time or daytime should be taken into account when defining the initial distribution of people onboard the ship. That is for night time scenarios one can specify that all passengers are in their cabins while their starting position for daytime scenarios will be distributed throughout the public spaces of the ship. In addition, one can specify a different distribution function of the response times for the night case and day case to account for the extra time needed to wake up passengers at night. One can also specify different evacuation procedures. A typical evacuation procedure on a cruise ship will be to first direct the passengers to their cabins to fetch their life jackets before they proceed to the muster station, whereas on a ro-ro passenger ship the most likely procedure will be to direct people straight to the mustering stations. This, as well as other custom defined evacuation procedures, can be specified prior to running the simulations.

3

Screenshots taken from the interactive demo version of maritimeEXODUS version 3.0.

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Fig. 4. Display of trim and heel with the maritimeEXODUS.

There are far more capabilities in current software than described above, and the various evacuation simulators might have chosen different solutions to account for various elements in an evacuation process. However, the ability to account for such effects as spread of fire and smoke, list conditions of the ship and the difference due to night and day scenarios will be important when performing evacuation simulations based on the evacuation scenarios presented in subsequent sections of this paper. 3. Critical accident scenarios There are two fundamentally different types of evacuation from a passenger ship, i.e. precautionary evacuations and emergency evacuations. A precautionary evacuation can be initiated in potentially dangerous situations even though there are no immediate threats to the people on board. Considering the risk associated with the evacuation process itself, the necessity of a precautionary evacuation will be thoroughly considered before it is initiated. In such situations, the time used in the evacuation process will not be critical and a typically precautionary evacuation scenario will be to direct the ship ashore and to abandon ship there. The characteristics of an emergency evacuation will be very different from that of a precautionary evacuation. In such circumstances the overall objective will be to muster as quickly as possible and to abandon the ship before it is too late. Failure to evacuate people in time will be fatal and the time spent escaping from the ship will be crucial. Such evacuations will typically only be carried out in case of a serious incident, such as a collision or grounding with subsequent water ingress or a fire that has escalated and run out of control. Regarding evacuation scenarios, precautionary evacuations are more or less covered by the primary MSC/Circ 1033 benchmark scenarios in that no restrictions apply to any of the escape route alternatives (IMO, 2002). The focus of the current study will thus be

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to construct novel evacuation scenarios describing emergency evacuations in different situations. It can be argued that it is not possible to take every thinkable accident scenario into account. However, it should not be necessary to cover all thinkable scenarios in order to gain an estimate of the overall level of risk. The aim is rather to identify some generic scenarios that represent the majority of the contributions to the overall risk level so that the contributions from other scenarios not directly covered will be negligible in comparison. It is hence assumed that a few wisely chosen generic evacuation scenarios will give a satisfactory estimate of the overall risk. As in all risk assessments, the results will be subject to uncertainties and if desired, the uncertainty connected to the selection of scenarios can be incorporated in a safety factor. However, further discussions of such a safety factor are considered out of scope of this paper. Based on the background material discussed in Section 2, a set of evacuation scenarios that are thought to be most relevant for evacuation simulations will be presented. The set of simulation scenarios corresponds to three types of accident scenarios, i.e. fire scenarios, collision scenarios and grounding scenarios. In the following these types of accidents will be discussed as well as their impact on the simulation scenarios. 3.1. Fire and explosion scenarios The probabilities of fire varied significantly from ro-ro passenger ships and cruise liners (Vanem and Skjong, 2004a). However, the statistics representing the distribution of different types of fires regarding origin, cause and development were similar. The main difference between the ship types is that ro-ro passenger ships contain enclosed car decks whereas cruise liners have laundry rooms, and these are potential areas for fires to start. In spite of these differences, generic scenarios representing both ro-ro passenger ships and cruise liners will be drawn up. These scenarios could be used for both types of ships, but the associated probability will depend on what type of ship is under consideration. The most common place on board a ship for a fire to start is in the engine room; between 60% and 70% of all fires on board passenger ships has its origin here.4 Between one out of three and one out of four of these fires will escalate and spread to other parts of the ship, while the remainder will be confined and extinguished within the engine room. Other places where fires are likely to occur are accommodation areas, public spaces and car decks or laundry rooms for ro-ro passenger ships and cruise liners respectively. Of these, fires in accommodation areas and public spaces are especially relevant to evacuation scenarios. A fire might trigger the initiation of an evacuation, and it may influence the evacuation performance in mainly two different ways. First, a fire might totally cut off some of the escape routes, e.g. corridors or stairways, so that alternative routes must be used. Secondly, smoke and poisonous gas produced in the fire might spread through the corridors and slow down people that use them for escape due to reduced visibility or difficulty to breathe. In addition a fire may have a psychological effect on the people onboard affecting their behaviour, causing e.g. panic, shock or paralysis of the passengers.

4

61% for ro-ro passenger ships and 68% for cruse vessels.

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Escape from the affected fire zone will normally be more critical than abandonment of the whole ship in case of fire. One important scenario will therefore be that people occupying the fire zone where a fire starts need to evacuate that fire zone to muster somewhere on the ship away from the fire. The time allowed for such evacuations should be rather short, as heat and smoke might be fatal in a few minutes. The most relevant fires in this case are fires that start in the accommodation areas or public spaces. An alternative fire scenario could be a fire that escalates and forces everyone onboard to abandon the ship. The time allowed for evacuation in this scenario will typically be quite long, but the fire might cut off some of the escape routes. Also in this type of evacuation scenario, the most critical issue will be whether or not people are able to escape the affected fire zone in time. All types of fires are relevant in this scenario. However, since fires starting in the accommodation areas and public spaces are simulated in greater detail in the previous scenario, these scenarios will be restricted to consider engine room fires that escalate. 3.2. Collision scenarios A collision will cause an emergency evacuation if there is a possibility that the ship will sink. Even though emergency evacuations may be initiated subsequent to a collision that does not cause the ship to sink, it is in situations where the ship actually sinks that the time consumed in the evacuation process is really critical. In a collision between two ships, it will generally be the struck ship that will sink as this receives the collision energy to the side, and in general one can assume that the struck ship will develop a list as it sinks. A relevant collision accident scenario will be a ship struck by another ship, resulting in flooding of more than two watertight compartments5 and finally sinking while developing a list. Estimates of probabilities related to collision of passenger ships as well as estimates of time to sink presented in Vanem and Skjong (2004b) will be used for developing these evacuation scenarios. 3.3. Grounding scenarios Grounding will cause an emergency evacuation if it is believed that the ship might sink, and the time used for evacuation will be critical if the ship actually goes down. The manner in which the ship sinks will also be important, and in Vanem and Skjong (2004b) it is distinguished between two different ways of sinking, i.e. sinking gracefully and sinking after capsizing. If the ship sinks gracefully, meaning that it will sink in an upright position, there will generally be enough time available for evacuation, and the decks of the ship will remain more or less horizontal. If the grounding causes the ship to capsize, however, the ship will generally sink much faster, and there will be an increasing list as the ship heals over to one side. When the list reaches some critical angel, e.g. 20, it will no longer be possible to abandon the ship using the lifeboats, and a large % of people still remaining on board are likely to perish.

5 Due to the current two-compartment standard applicable to passenger ships according to SOLAS (IMO, 2001b).

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For grounding accidents, one are thus left with two relevant accident scenarios. The first scenario describe a passenger ship that runs aground and subsequently sinks in a gracefully manner. The second scenario corresponds to a ship that capsizes after grounding, and describes a passenger ship that sinks with a gradually increasing list until evacuation is no longer possible. Estimates of probabilities and time to sink that will be used are presented in Vanem and Skjong (2004b). 4. Evacuation scenarios The accident scenarios presented in the previous chapter cannot be utilized directly by an evacuation simulator. In order to convert the scenarios into well-defined benchmark evacuation scenarios, one must determine how to parameterize the evacuation scenarios according to Fig. 1 and combine them into a complete set of evacuation scenarios. In this section this process will be outlined and the resulting set of benchmark evacuation simulations will be presented. 4.1. Initial distribution of passengers and crew The initial distribution of passengers and crew are not dependent on the accident leading to the evacuation. Two alternative initial distributions are suggested in the MSC benchmark scenarios (IMO, 2002) and these are assumed appropriate. These should be coupled with each of the evacuation scenarios described in the following, leading to two variants of each of the scenarios: one for the day case and one for the night case. This is illustrated in Fig. 5. The night and day cases vary in initial distributions of the passengers and crew, but also have different characteristics regarding response times. 4.2. Effects of weather and sea state The weather and sea state will have an impact on the shipÕs movement and heavy weather with rough seas can delay the evacuation performance noticeably. This suggests that the weather and sea should be included in an evacuation scenario. Two different

Day case

Evacuation Scenario A

Night case

Evacuation Scenario B

Day case

Evacuation Scenario C

Night case

Evacuation Scenario D

Day case

Evacuation Scenario E

Night case

Evacuation Scenario F

Evacuation Scenario 1

Evacuation Scenario 2

Evacuation Scenario 3

Fig. 5. Coupling evacuation scenarios with initial distributions of passengers.

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weather cases could be constructed, i.e. good weather and bad weather, and these could be coupled to the evacuation scenarios in much the same way as the day and night case was. However, for the purpose of this study, the impact of the weather and sea state on the evacuation performance will be neglected in the scenarios. 4.3. Precautionary evacuation Precautionary evacuations are initiated in case an incident should have the potential to develop into a serious accident. In these evacuations one can assume that there will be no fire or smoke causing obstructions in the escape routes or list or trim due to collision or grounding. A precautionary evacuation thus corresponds to the primary evacuation cases proposed in the MSC benchmark scenarios (IMO, 2002). Such evacuation simulations will measure the evacuation performance associated with a proposed design under ideal conditions and cannot be mapped to any specific accident. The simulation results will solely be the time consumed before everyone was successfully evacuated and this time and can be compared to some desired or maximum evacuation time. The outcome of such evacuation simulation will not consist of any number of fatalities and precautionary evacuations will thus not contribute to the estimated risk. 4.4. Emergency evacuation The main scope of the current study is to develop evacuation scenarios corresponding to realistic passenger ship accidents. In Section 3, three groups of relevant accident scenarios were identified that should be mapped to evacuation scenarios as summarized in Table 2. The identified accident scenarios can hence be represented by five evacuation scenarios. However, the collision evacuation scenario is similar to one of the grounding evacuation scenarios, and these could be merged into one evacuation scenario—evacuation from sinking ship that develops list. Four different emergency evacuation scenarios thus remain, all associated with different probabilities (presented in terms of per shipyear). The first evacuation scenario, escaping from a fire zone, is associated with the probability of a fire starting in a public space or accommodation area. This was investigated in Vanem and Skjong (2004a): 3 P ro-ro and P cruise  1:2  102 fire  1:9  10 fire Approximately 20% of the fires start in accommodation areas or public spaces, and these are the fires associated with the first evacuation scenario. The probabilities associated with this scenario will thus be:

P ro-ro Scenario

1

 3:8  104 and P cruise Scenario

1

 2:4  103

Table 2 Relevant accident scenarios and associated evacuation scenarios Accident scenarios

Evacuation scenarios

Fire accidents

Escaping from a fire zone (accommodation area/public space) Abandoning ship with escalating fire (engine room fires) Evacuation from sinking ship developing list Evacuation from sinking ship developing list Evacuation from ship sinking gracefully

Collision accidents Grounding accidents

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The second scenario covers fires that escalates and causes abandonment of the ship at sea. Fires starting anywhere onboard the ship contributes to this scenario, but since 20% of the fires are extracted for study in the first evacuation scenario, only the remaining 80% of the fires are contributing to the second. According to the event trees in Vanem and Skjong (2004a), about 15% of the fires escalates and causes an emergency evacuation at sea (13.8% for cruise liners and 15.0% for ro-ro passenger ships), giving the following probabilities: P ro-ro Scenario

2

 2:9  104 and P cruise Scenario

2

 1:8  103

The third evacuation scenario, evacuation from a ship sinking while developing list, have contributions from two different accident scenarios, i.e. collision and grounding. From the results presented in Vanem and Skjong (2004b), one can find the contributions from collision and grounding to this evacuation scenario: 6.2 · 104 from collisions and 5.2 · 105 from grounding, adding up to: P Scenario

3

 6:7  104

This scenario is actually a composite of different scenarios where ships sink with different speeds. Ships that sink within a few minutes and ships staying afloat for more than an hour after the initial event are covered by this scenario. How rapidly the ship will sink is associated with a probability distribution and this was estimated in the Vanem and Skjong (2004b). These results are used in order to find the average probability distribution for the time to sink, as presented in Table 3. Finally, the fourth and last evacuation scenario corresponds to evacuation from a ship that sinks gracefully subsequent to grounding. This scenario is associated with the following probability (Vanem and Skjong, 2004b): P Scenario

4

 5:8  105

An estimate of how rapidly the ship will sink is obtained, as presented in Table 4. All the possible accidents can occur either at daytime or night time. Assuming people sleep approximately 8 h a day in average, and that the exposure to such accidents are uniformly distributed in time, this corresponds to a probability factor of 2/3 and 1/3 for the day case and night case of the evacuation scenarios respectively. Table 5 contains the probabilities (per shipyear) associated with the proposed evacuation scenarios. A total of eight evacuation scenarios, in addition to the precautionary evacuation scenario, are proposed for use in the simulations and these will be described by defining the four main evacuation scenarios in the first column of Table 5.

Table 3 Probabilities of sinking or capsizing within different times Time (min)

<5

5–10

10–15

15–30

30–60

60–90

>90

Probability

0.18

0.19

0.20

0.18

0.13

0.07

0.05

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Table 4 Probabilities of sinking within different times Time (min)

<5

5–10

10–15

15–30

30–60

60–90

>90

Probability

0.02

0.08

0.15

0.22

0.16

0.3

0.07

Table 5 Complete set of evacuation scenarios with associated probabilities Main evacuation scenario

Case

Escaping from a fire zone

Day

Escaping from a fire zone at daytime

Night

Escaping from a fire zone at night

Day

Abandoning ship on fire at daytime

Night

Abandoning ship on fire at night

Evacuation from sinking ship, listing

Day Night

Evacuation, sinking ship listing, daytime Evacuation, sinking ship listing, night

4.5 · 104 2.2 · 104

Evacuation from sinking ship, upright

Day Night

Evacuation, sinking ship upright, daytime Evacuation, sinking ship upright, night

3.9 · 105 1.9 · 104

Precautionary evacuation

Day Night

Precautionary evacuation at daytime Precautionary evacuation at night

Abandoning ship on fire

Resulting evacuation scenario

Probability Ro-ro Cruise Ro-ro Cruise

2.5 · 104 1.6 · 103 1.3 · 104 8.0 · 104

Ro-ro Cruise Ro-ro Cruise

1.9 · 104 1.2 · 103 9.7 · 105 6.0 · 104

4.5. Proposed benchmark scenarios Four main evacuation scenarios based on possible accidents have been outlined in addition to a precautionary evacuation scenario. In order to ensure unambiguous use of these scenarios, the scenarios need to be defined in more detail. 4.5.1. Main Scenario 1—escaping from a fire zone With this evacuation scenario, only parts of the vesselÕs total layout are considered at a time. Specifically, the simulations based on this scenario should be run separately for each fire zone on the vessel containing passenger accommodation areas or public spaces to ensure that the escape arrangements are adequate for quick evacuation of that particular fire zone. The simulation will start when the evacuation is initiated, corresponding to the mustering alarm, and end when the evacuees are exiting from the fire zone. Prior to running simulations based on this scenario, a reasonable population of passengers and crew should be distributed throughout the whole vessel in accordance with what is previously described in this report. This distribution should be kept unchanged for a set of simulations run for each fire zone to ensure consistency. Prior to actuating the simulations, a specific position should be defined as the source of a developing fire in the fire zones under consideration. After completion of a full cycle of simulations, i.e. all the fire zones of the ship, an alternative distribution of passengers can be applied and new places can be chosen as starting place of the fire, and the simulations can be repeated. After successive cycles of simulation

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Table 6 Input and output for main Scenario 1 Required input

Expected output

Overview of total ship layout Detailed layout of relevant fire zones Initial distribution of passengers and crew Starting point of fire within each fire zone

Average evacuation time for each fire zone Maximum evacuation time for each fire zone Minimum evacuation time for each fire zone Number of fatalities for each fire zone

runs, the output from the simulations for each fire zone will form a distribution of evacuation times and number of fatalities and this distribution can be used to extract mean values of average evacuation time, maximum and minimum evacuation times as well as expected number of fatalities. The required input and output for this scenario are summarized in Table 6. 4.5.2. Main Scenario 2—abandoning a ship on fire Simulations based on this evacuation scenario considers the entire vesselÕs layout and model a complete evacuation process from it is initiated until it is ended with everyone safely evacuated or deceased. A reasonable initial distribution of passengers should be applied and a point of origin should be defined for the fire. It should be kept in mind that fires starting in accommodation areas or public spaces are already accounted for in main evacuation Scenario 1, thus the starting point of the fires should be either in the engine room, in the car deck of ro-ro ferries, in the laundry room of cruise liners or other similar areas. Each simulation run will result in a set of evacuation times for the passengers as well as number of fatalities. Several simulations should be run for the same initial distribution of the population and with the same starting point of the fire. In this way one will obtain a distribution function of the output, so that mean values of the average, maximum and minimum evacuation times as well as number of fatalities can be extracted. As stated in Section 3.1, the time available for evacuation is expected to be quite long in this scenario and most fatalities are expected to occur due to exposure to smoke and heat. The required input and output from simulations based on this scenario is summarized in Table 7. 4.5.3. Main Scenario 3—evacuation from a sinking ship developing list The third scenario describes a ship sinking while developing a list until it capsizes and sinks. The entire ship will be considered and the effect on the evacuation performance of the list should be accounted for. For simplicity, it will be assumed that the list is increasing constantly as a function of time.

Table 7 Input and output for main Scenario 2 Required input

Expected output

Layout of entire vessel Initial distribution of passengers and crew Starting point of the fire

Average evacuation time Maximum evacuation time Number of fatalities

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Table 8 Input and output for main Scenario 3 Required input

Expected output

Entire vessel layout

Number of people successfully evacuated as a function of evacuation time Number of people still not evacuated by the cut-off time

Initial distribution of crew and passengers List direction (starboard/port) Maximum list angle (when further evacuation becomes impossible. Default = 20) Cut off time for the simulation (corresponding to vessel going down). Normally, T = 60 min

This scenario is a composite of several scenarios: One scenario where the ship sinks after 5 min, one where the ship sinks after 10 min etc. Each time to sink is associated with a probability as presented in Table 3. In order to accommodate all this different accident scenarios into one evacuation scenario, a generic capsizing scenario is needed to represent them all. It is assumed that using a scenario with relatively slow sinking will be appropriate, and the consequences of ships sinking faster can be found from investigating how many people were still not safely evacuated by this time. For the purpose of this study, a cut-off time of 60 min will be assumed, corresponding to the maximum allowed evacuation time according to the SOLAS regulations (IMO, 2002). The entire vessel layout must be available for this scenario and the initial distribution of passengers and crew must be specified. In addition, the direction of list should be defined, e.g. to port or starboard, and the maximum angle of list that still renders evacuation of that particular ship possible should be entered. 20 can be used as a default value as this corresponds to the requirements for launching survival craft (IMO, 2001b). In this scenario, no additional hazards will be present, and people are not expected to perish during the evacuation process itself. The fatalities will only be the ones still not successfully evacuated by the time the ship sinks. The output from the simulations should therefore be number of people successfully evacuated as a function of the evacuation time. One can then couple this output with the probabilities of different time to sink in Table 3 to find the risk associated with this scenario. The required input and output associated with this scenario is given in Table 8. 4.5.4. Main Scenario 4—evacuation from a gracefully sinking ship This scenario corresponds to a ship sinking in an upright position following a grounding accident. The evacuation scenario will resemble main Scenario 3 apart from not developing list. Prior to running the simulations, one must know the layout of the vessel and the initial distribution of passengers. As the ship is sinking gracefully, the sinking will not have any significant effect on the evacuation and no such effects need to be accounted for. The simulations should result in a distribution describing how many people have successfully been evacuated as a function of the evacuation time. This can be coupled with the probabilities of sinking within a certain time presented in Table 4 to estimate the total risk associated with this scenario. The required input and output from simulations run over this scenario is given in Table 9.

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Table 9 Input and output for main Scenario 4 Required input

Expected output

Entire vessel layout Initial distribution of passengers and crew

Number of people successfully evacuated as a function of the evacuation time

Table 10 Input and output for the precautionary evacuation scenario Required input

Expected output

Entire layout of the vessel

Total evacuation time (time before all people are successfully evacuated) Identification of possible congestions along the escape routes

Initial distribution of crew and passengers

4.5.5. Precautionary evacuation scenario In addition to the evacuation scenarios corresponding to an accident scenario, a precautionary evacuation scenario is suggested that considers evacuation from the ship in the absence of accidents. This evacuation scenario will be identical to the primary MSC benchmark scenarios (IMO, 2002) and the required input is the layout of the vessel and the initial distribution of passengers. The results from simulations run over this scenario will not add to the risk associated with evacuation from passenger ships. No hazards are present and naturally no fatalities will occur. However, such simulations can be used for studying possible bottlenecks or congestions in an evacuation process and the shipÕs design of escape routes can be evaluated; i.e. its effect on the total evacuation time can be measured. The input and output requirements for simulations of precautionary evacuation scenarios are summarized in Table 10. 5. Calculating the risk from simulation results The total risk associated with different situations of evacuation from a particular ship can be found from the simulation results. Each evacuation scenario will contribute to this risk and in the following, a structured methodology for estimating the overall risk associated with a passenger ship based on the simulations will be outlined. The first main scenario considers fires in the accommodation areas or public spaces of the ship and each fire zone is investigated individually. A number of simulations will be run for each fire zone and the outcome of the simulations will provide an estimate of the expected number of lives lost in a possible fire for each fire zone. Assuming that fires are evenly distributed among the fire zones, the average of the expected fatalities for all the fire zones can be chosen to represent the expected number of fatalities in a fire in the accommodation areas or public spaces of the ship.6 Multiplying these expected number of fatalities with the probabilities associated with the scenarios, one arrives at an estimate 6 Alternatively, the highest number of fatalities from one of the fire zones should be used in order to gain a conservative estimate of the risk contribution from this scenario.

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of the risk contribution for this scenario in terms of fatalities per year for the ship subject to the study. The second main scenario considers the entire ship and simulates abandonment from a ship due to an escalating fire. It is assumed that the time available for evacuation is sufficiently long to allow everyone the time needed for evacuation, and the only fatalities are thus those dying from exposure to heat or smoke. Running simulations over this scenario will result in an estimate of total number of fatalities on the entire ship for the different cases. Fig. 6 shows an example of such simulation results from the maritimeEXODUS software. These estimates represent the expected consequences and multiplied by the probabilities associated with the scenarios, an estimate of the contribution to the total risk from these scenarios is obtained, in terms of fatalities per year. Contributions to the risk from the third and fourth main scenarios will be people going down with the ship, i.e. people not able to evacuate the ship in time. The expected number of fatalities can be calculated from the simulation output and the time to sink probabilities given in Tables 3 and 4. One outcome from the simulations run over these scenarios will be the number of people successfully evacuated as a function of the evacuation time. An example of such output from the maritimeEXODUS software is shown in Fig. 7. Examining this graph, one can obtain an estimate of how many people have successfully been able to evacuate the ship after e.g. 5 min. The total population, in this case

Fig. 6. Simulation output example—total number of fatalities in a fire scenario.

Fig. 7. Simulation output example—people evacuated as a function of evacuation time.

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Table 11 Example of consequence associated with Scenario 3 Time (min)

<5

5–10

10–15

15–30

30–60

60–90

>90

Probability Fatalities Risk contribution

0.18 530 95

0.19 420 80

0.20 290 58

0.18 90 16

0.13 0 0

0.07 0

0.05 0 Total 249

540 people, minus this number will still be on board on the ship after five minutes, and the probability of the ship sinking within 5 min (from Tables 3 and 4) corresponds to the probability of this number of fatalities. Using the graph in Fig. 7 as an example, one can estimate that if the ship sinks within five minutes, 530 people will be killed, 420 people if the ship sinks within 10 min, 290 if it sinks within 15 min, 90 if it sinks within 30 min and none if the ship sinks after 60 min. Assuming this was a day case of Scenario 3, these numbers can be coupled with the probabilities in Table 3 to get the total number of fatalities as shown in Table 11. In other words, the day case of Scenario 3 has an estimated consequence of 249 fatalities, and according to Table 5 the probability of this is 4.5 · 104 per year. This gives the total risk contribution from this scenario: RiskDay,3 = 0.11 fatalities per year. Similar calculations should be carried out for the night case and for the two cases of Scenario 4. When the risks for all scenarios have been successfully calculated, the total risk associated with the design alternative subject to the analysis will be the sum of these, i.e. Eqs. (1) and (2) concretise into: Risk ¼ RiskDay;Scenario 1 þ RiskNight;Scenario 1 þ


þ RiskNight;Scenario X ¼ Riski;Scenario j

4

ð3Þ

i¼Day;Night j¼14

6. Safety regulations and evacuation simulations Evacuation analyses is a requirement for new ro-ro passenger ships (IMO, 2001a) and it is believed to be cost-effective and time-saving to perform such analyses utilizing computer simulation software. Evacuation simulations can also be a useful tool beyond the minimum requirements imposed by the SOLAS regulations. Evacuation simulations can be used to investigate the escape arrangements of a specific ship and to ensure that the shipÕs design allow for swift evacuation in an emergency situation. Realizing that different types of accidents may lead to evacuation of the ship, different evacuation scenarios should be used in successive simulations, analysing different aspects of an evacuation, e.g. evacuation in the presence of fire and smoke or evacuation from a ship developing list. When the design of a new ship is examined, evacuation simulations should be carried out in two steps. First, the precautionary evacuation scenario will be used to study the evacuation with no hazards present. This will reveal potential bottlenecks along the escape routes and estimate the maximum time consumed by the evacuation process. This estimated evacuation time will then be compared to prevailing requirements regarding maximum permitted evacuation time. This step is equivalent to present safety regulations,

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where approval of the design will be granted if requirements regarding total evacuation time are met. The next step would be a more comprehensive study of the risk associated with evacuation of that particular ship. The complete set of eight evacuation scenarios should be used, as outlined in Section 4, and the risk will be estimated as described in Section 5 in order to gain an estimate of the total risk associated with evacuation. Different design options will give different overall risks and the alternative associated with the lowest risk can easily be identified. In a truly risk-based regulatory regime, a development towards approval based on a holistic approach to risk and a fundamental understanding of the overall risk level is suggested. In such a regime, it would not be sufficient to meet certain performance criteria, e.g. total evacuation time, without knowing the impact this has on the total risk. More important than meeting such performance criteria it would be to meet fundamental criteria on risk, i.e. it should be demonstrated that the overall risk level fulfils defined risk criteria. In order to facilitate such a risk-based regulatory regime to emerge, there is a need for an unambiguous way to link the evacuation performance criteria to the overall risk, and the set of evacuation scenarios proposed in this paper constitutes such a link. Hence, approval can be based on the following requirements, where the risk is calculated from Eq. (3) and appropriate probabilistic risk acceptance criteria are established based on a sound rationale (Norway, 2000; Skjong and Eknes, 2001; Skjong and Vanem, 2004): Risk 6 Risk criteria

ð4Þ

This approach is completely aligned with recent trends of employing the principle of equivalent safety to stimulate innovative but safe design of new ships (IMO, 2001d), although it goes a bit further. Current practice for demonstrating equivalent safety of a design deviating from prescriptive regulations is to evaluate certain performance factors, e.g. evacuation time, without explicitly considering the overall risk. With the approach described in this paper, however, it is proposed to move one step further: To base approval on compliance with high-level, risk based criteria. The fundamental relationship between the different criteria is illustrated in Fig. 8 where the risk based, performance based and prescriptive criteria are seen as different levels of abstraction and technical detail of equivalent design requirements. However, the translation of the criteria should be considered very carefully in order to ensure that the safety level corresponding to the different criteria are indeed equivalent. In general, a set of prescriptive criteria should be in accordance with a required minimum performance of the system or arrangement to which they apply, and thus correspond to appropriate performance criteria. Furthermore, the required performance of various subsystems or components should be related to the overall risk level associated with the complete design (i.e. ship). Compliance with a set of prescriptive criteria should thus ensure that a certain level of risk is not exceeded and the prescriptive regulations should be anchored in a basic understanding of the total risk. In the reverse direction, risk based criteria will dictate restrictions on the acceptable performance of the system. Furthermore, performance criteria will imply technical restrains on the possible solutions of a design problem and thus suggest a set of prescriptive criteria. However, different physical implementations and technical solutions might result in the same performance. Alternative design not complying with the prescriptive rules might thus result in equivalent performance and hence an equivalent level of safety as solutions that

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Fig. 8. Relationship between risk based, performance based and prescriptive design criteria.

comply with the rules. In principle, therefore, risk based, performance based and prescriptive criteria should be interchangeably related to one another, although this requires consistency and holistic thinking in the rule developing process. With the proposed approach, approval will be based on high-level, risk based criteria, and the evacuation simulations utilizing the proposed set of evacuation criteria, will link the technical design solutions to the overall risk-level of the ship. 7. Conclusions Mainly motivated by the IMO requirements that all new ro-ro passenger ships shall perform an evacuation analysis early in the design phase, much effort have been invested in developing advanced ship evacuation simulation software. Even though the IMO regulations accept simplified analyses carried out by hand, advanced evacuation simulations utilizing sophisticated ship evacuation software and computer power for calculations are considered to be a time-saving and cost effective option. Use of such software is thus believed to be the preferable choice for carrying out evacuation analyses in the future. Prior to executing ship evacuation simulations for a particular vessel, there is a need for a set of standardised evacuation scenarios that these simulations can utilize and run over. These scenarios should cover the major hazards associated with evacuation of the ship and amount to a complete set of scenarios. The Maritime Safety Committee within the IMO has proposed a few benchmark scenarios but these scenarios cannot easily be mapped onto real accident scenarios and does therefore not represent any particular hazards. Because of this a new set of evacuation scenarios have been developed. Based on the MSC/Circ. 1033 benchmark scenarios and a recent risk assessment of passenger ship evacuation, this paper proposes a new set of evacuation scenarios to be used in evacuation simulations. The development of the scenarios has been presented as well as the coupling between the evacuation scenarios and accident scenarios and between the

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evacuation scenarios and the overall risk level associated with the ship. In addition, required input and output from the simulations is described. Finally, possible future developments of the maritime safety regulations have been discussed, i.e. it has been demonstrated how the proposed set of scenarios will facilitate the emergence of truly risk based probabilistic safety regulations. Acknowledgement This study has been supported by the FIRE EXIT project, funded by the European Community under the ‘‘Competitive and Sustainable Growth’’ Programme, Project Number: GRD2-2001-50055 and Contract Number: G3RD-CT-2002-00824, FIRE EXIT. References Caldeira-Saraiva, F., Gyngell, J., Wheeler, R., Galea, E., Carran, A., Skjong, R., Vanem, E., Johansson, K., Rutherford, B., Re´, A.J.S., 2004. Simulation of ship evacuation and passenger circulation. In: Proceedings of the 2nd International Maritime Conference on Design for Safety, Osaka, Japan, October 27–30, 2004. Galea, E.R., Gwynne, S., Lawrence, P.J., Filippidis, L., Blackshields, D., 2004. maritimeEXODUS V4.0 User guide and technical manual, fire safety engineering group. University of Greenwich, UK. Gwynne, S., Galea, E.R., Owen, M., Lawrence, P.J., 1999. An investigation of the aspects of occupant behaviour required for evacuation modeling. Journal of Applied Fire Science 8 (1), 18–59. IMO, 2001a. SOLAS Amendments 2000. International Maritime Organization, London, UK, ISBN 92-801-5110X. IMO, 2001b. SOLAS Consolidated Edition 2001. International Maritime Organization, London, UK, ISBN 92801-5100-2. IMO, 2001c. FSS code international code for fire safety systems. International Maritime Organization, London, UK 2001, IMO Publication: IMO-155E, ISBN: 92-801-5111-8. IMO, 2001d. Guidelines on alternative design and arrangements for fire safety. IMO MSC/Circ. 1002, International Maritime Organization, London, UK, 2001. IMO, 2002. Interim guidelines for evacuation analyses for new and existing passenger ships. IMO MSC/Circ. 1033, International Maritime Organization, London, UK, 2002. Lee, D., Kim, H., Park, J.-H., Park, B.-J., 2003. The current status and future issues in human evacuation from ships. Safety Science 41 (10), 861–876. Norway, 2000. Formal safety assessment, decision parameters including risk acceptance criteria—submitted by Norway. IMO MSC 72/16, International Maritime Organization, London, UK, 2000. Skjong, R., Eknes, M., 2001. Economic activity and social risk acceptance. In: Proceedings of European Safety & Reliability Conference, ESREL 2001, Torino, Italy, September 16–20, 2001. Skjong, R., Vanem, E., 2004. Optimised use of safety interventions. In: Proceedings of the Joint International Conference on Probabilistic Safety Assessment and Management—European Safety & Reliability Conference, PSAM 7—ESREL 2004, Berlin, Germany, June 14–18, 2004. UK, 2004. Recommendations on evacuation analysis for new and existing passenger ships, data available as input to ship evacuation simulation tools—submitted by the United Kingdom. IMO FP 49/INF.8, International Maritime Organization, London, UK, 2004. Vanem, E., Skjong, R., 2004a. Fire and evacuation risk assessment for passenger ships. In: Proceedings of the 10th International Fire Science and Engineering Conference (Interflam) 2004, vol. 1. Edinburgh, Scotland, July 5–7, 2004, pp. 365–374, ISBN 0 9541216-4-3. Vanem, E., Skjong, R., 2004b. Collision and grounding of passenger ships—risk assessment and emergency evacuations. In: Proceedings of the 3rd International Conference on Collision and Grounding of Ships, ICCGS 2004, Izu, Japan, October 25–27, 2004. Yoshida, K., Murayama, M., Itakaki, T., 2001. Study on evaluation of escape route in passenger ships by evacuation simulation and full-scale trials. In: Proceedings of the 9th International Fire Science and Engineering Conference (Interflam) 2001, vol. 2. Edinburgh, Scotland, September 17–19, 2001, ISBN 0 9532312-7-5.

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