4.1. Societal risk
The societal risk in computed based on the calculated individual risk frequencies. Integrating the probability of death for each event with the population specified Nu, represents the number of people killed by a given event. Fig. 11 illustrates the modelled risk level for cruise ships in the F–N diagram. The risk level is calculated as the sum of the frequency per ship year for analysed accidents. Although notable accidents occurred in recent years, these did not influence the statistics of accidents much. The consequent Risk control options taken into consideration by the international community allowed the reduction of the tolerable risk by a factor of 3, from 4.9 × 10−2 to 1.57 × 10−2 fat/year. Fig. 11 shows the calculated tolerable risk limit for 2014, based on the calculation procedure of IMO FSA. Assuming this limit as a total risk limit the societal risk would be elevated and additional control actions would be required. As noted above the risk limit is not only a calculated value, but also a matter for company and country policy