The amount of assumed accumulated water on deck may, in addition to any reduction in accordance with paragraph 1.1, be reduced for operations in geographically defined restricted areas. These areas are designated in accordance with the significant wave height (h_s) defining the area in line with the provisions of Article 5 of this Directive.

If the significant wave height (hs), in the area concerned, is 1,5 m or less then no additional water is assumed to accumulate on the damaged ro-ro deck. If the significant wave height in the area concerned is 4,0 m or more then the height of the assumed accumulated water shall be the value calculated in accordance with paragraph 1.1. Intermediate values to be determined by linear interpolation (see figure 3).

The height h_w is kept constant, therefore the amount of added water is variable as it is dependent upon the heeling angle and whether at any particular heeling angle the deck edge is immersed or not (see figure 4). It should be noted that the assumed permeability of the car deck spaces is to be taken as 90 % (MSC/Circ.649 refers), whereas other assumed flooded spaces permeabilities are to be those prescribed in the SOLAS Convention.

If the calculations to demonstrate compliance with this Directive relate to a significant wave height less than 4,0 m that restricting significant wave height must be recorded on the vessel's passenger ship safety certificate.