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The International Maritime Organization (IMO) is revising the Intact Stability Code. The so-called second generation intact stability criteria will provide additional safety measures against stability failures in waves. The draft regulations for three failure modes, parametric roll, pure loss of stability and surf-riding/broaching are reviewed and sample calculations for a fast RoPax ship are presented. The main emphasis is on the sensitivity of the results to the applied input data, which is not very accurate in the initial design phase. The implementation and effects of the new calculations to the ship design are discussed.

While the development of stability regulations mainly has been driven by the needs for passenger ships, cargo ships are also getting an update in the newly adopted amendments to the Safety of Life at Sea (SOLAS) convention. The stability at intermediate flooding stages have previously been ignored for cargo ships, but if the ship is equipped with cross-flooding devices, intermediate filling phases will now be evaluated. In this study, the relevancy of these intermediate stages for cargo ships is investigated. The focus is on a case study of a short sea ro-ro cargo ship with cross-flooding ducts in the double bottom. In addition to the conventional regulatory calculation methods, also time-domain flooding simulation is used for realistic assessment of intermediate stages and the actual time-to-flood. Such tools have previously been used for damage stability analyses of passenger ships. The different calculation methods are compared against each other through the attained subdivision index. The results indicate that cross-flooding improves damage stability also for cargo ships, and that simulation is an applicable tool also for design and analysis of safer ships.