Safe Return to Port (SRtP) regulation entry into force introduced new concepts and requirements for large passenger ships (constructed on or after 1st July 2010, having length of 120 meters or more, or having three or more Main Vertical Zones) deeply affecting their design. In fact, the need of assuring a certain level of service also in case of fire or flooding events (within certain limits) caused a revolution in systems' design, mainly due to the relevance assumed by the systems' onboard placement. In this paper, motivations and basic concepts of SRtP are explained. A discussion about direct and indirect impacts on design process of such a regulation is then given, focusing in particular on the onboard power system, along with some examples of practical design and building issues.
