4.5 Required Subdivision Index R^footnote:

 (1) The subdivision of a ship is considered sufficient if the attained subdivision index A, determined in accordance with section 4.6, is not less than the required subdivision index R calculated in accordance with this regulation and if, in addition, the partial indices A_s, A_p and A_l are not less than 0.9R for passenger ships.

(2) For all passenger ships to which the damage stability requirements of this Chapter apply, the degree of subdivision to be provided shall be determined by the required subdivision index R, as follows-

• where:

• N = N₁ + 2N₂;

• N₁ = number of persons for whom lifeboats are provided^footnote; and

• N₂ = number of persons (including officers and crew) the ship is permitted to carry in excess of N₁.

(3) Where the conditions of service are such that compliance with subsection (2) on the basis of N = N₁ + 2N₂ is impracticable and where the Administration considers that a suitably reduced degree of hazard exists^footnote, a lesser value of N may be taken but in no case shall the value be less than N = N₁ + N₂.