3 Method of evaluation

 The steps in the evacuation analysis are:

  3.1 Description of the system

• .1 Identification of assembly stations.

• .2 Identification of embarkation stations, MES and survival craft.

• .3 Description of the evacuation procedure including the role of the crew.

• .4 Identification of groups and their escape route.

  3.2 Assumptions

This method for estimating evacuation time is basic in nature and, therefore, common evacuation analysis assumptions should be made as follows:

• .1 passengers and crew should carry out the evacuation in a sequence of groups according to the evacuation procedure;

• .2 passengers and crew will evacuate via the primary escape route;

• .3 walking speed depends on the type of escape facility, assuming that the flow is only in the direction of the escape route, and that there is no overtaking;

• .4 passengers' disabilities or medical conditions that will severely hamper their ability to keep up with the flow are neglected (see paragraph 3.2.8.1 below);

• .5 passenger load is assumed to be 100% (full load);

• .6 full availability of escape arrangements is considered;

• .7 people can move unhindered;

• .8 the allowable evacuation time as per section 4.8.1 of the 2000 HSC Code is given by (min), where:

  • .8.1 division by 3 accounts for the safety factor, which includes passengers' ages and disabilities, restricted visibility due to smoke, effects of waves and craft motions on deployment, travel and embarkation time and of violations to the evacuation procedure;

  • .8.2 subtraction of 7 min accounts for initial detection and extinguishing action (section 4.8.1 of the 2000 HSC Code); and

  • .8.3 for category B craft, the passenger awareness time, the time needed for passengers to reach assembly stations and the time needed for manning emergency stations is included in the 7 min time (see section 4.8 of the 2000 HSC Code);

• .9 as the evacuation procedure is designed to carry out evacuation under controlled conditions (section 4.8.1 of the 2000 HSC Code), no counter flow takes place; and

• .10 when using table 3.6 it is assumed that at the beginning of the evacuation, passengers are located at a distance not greater than two decks from the embarkation station.

  3.3 Scenarios to be considered

• 3.3.1 For the purpose of calculating the evacuation time in category A craft, passengers should be assumed to be distributed in a normal voyage configuration (section 4.8.4.1 of the 2000 HSC Code).

• 3.3.2 For the purpose of calculating the evacuation time in category B craft, passengers and the crew should be assumed to be distributed among assembly stations and be ready for embarkation (section 4.8.4.2 of the 2000 HSC Code).

  3.4 Performance standards

• 3.4.1 The following two performance standards should be complied with for calculating the overall evacuation time:

  	(3.4.1.1)
  	(3.4.1.2)

• 3.4.2 Both performance standards are derived from section 4.8.1 of the 2000 HSC Code.

  3.5 Calculation of t_E and t_M

• 3.5.1 The values of t_E and t_M should be calculated separately based on an appropriate combination of the following documented and independently witnessed trials as is acceptable to the Administration but which may be subject to verification trials:

  • .1 type approval trials^footnote for any inflatable liferafts and marine evacuation systems used for the evacuation of the craft, the relevant deployment and embarkation times being increased by factors of 1.3 and 1.14, respectively; and

  • .2 full scale shipboard trials on closely similar craft and evacuation systems.

• 3.5.2 Safety factors on t_E and t_M are accounted for by dividing by 3 in performance standards formulae (3.4.1.1) and (3.4.1.2).

  3.6 Calculation of t_I

• 3.6.1 Parameters to be considered:

  • .1 clear width, W_c , is:

    • .1 measured off the handrail(s) for corridors and stairways;

    • .2 the actual passage width of a door in its fully open position;

    • .3 the space between the fixed seats for aisles in public spaces; and

    • .4 the space between the most intruding portions of the seats (when unoccupied) in a row of seats in public spaces;

  • .2 speed of persons, S (m/s) is the speed of evacuees along the escape route (table 3.6 provides the values of S which should be used for the analysis);

  • .3 specific flow of persons, F_s (p/(m/s)), is the number of evacuating persons past a point in the escape route per unit time per unit of clear width W_c (table 3.6 provides the values of F_s which should be used for the analysis).

  • .4 calculated flow of persons, F_c (p/s), is the predicted number of persons passing a particular point in an escape route per unit time. It is obtained from:

    (3.6.1.4)

  • .5 flow time, t_F (s), is the total time needed for a group of N persons to move past a point in the egress system. It is calculated as:

    (3.6.1.5)

  • .6 walking time, t_w (s), is the total time needed for a person to cover the distance between the assembly station and the embarkation station.

• 3.6.2 Transitions

  Transitions are those points in the egress system where the type of a route changes (e.g. from a corridor to a stairway) where routes merge or branch out.

• 3.6.3 Procedure for calculation of t_I is as follows:

  • .1 Groups of people:

    For the purposes of evacuation, the total number of persons on board is broken down into one or more groups of people. It should be assumed that all persons in a group carry out the evacuation at the same time, along the same route and towards the same embarkation station. The number of persons in each group, the number of groups and the embarkation station assigned to each group should be in accordance with the evacuation procedure.

  • .2 Schematic representation:

    The escape routes from assembly stations to embarkation stations are represented as a hydraulic network, where the pipes are the corridors and stairways, the valves are the doors and restrictions in general.

  • .3 For each foreseen group of people:

    • .1 The walking time, t_w, is calculated by using the speed of persons specified in table 3.6 and the distance between the pertinent assembly and embarkation stations.

    • .2 The flow time, t_F, of each portion of the escape route is calculated using the specific flow F_s from table 3.6 and the appropriate clear width of that portion of escape route. The total flow time is the largest value obtained.

    • .3 The travel time is obtained as the sum of the walking time and the total flow time.

• 3.6.4 Ideal travel time t_I

  Calculations as per paragraph 3.6.3.3 should be repeated for each foreseen group of people. The highest resulting travel time is then taken as the ideal travel time for use in performance standard in paragraph 3.4.