Figure 4.1.20 Integrating ice index v.s. freight cost of 50BC
As can be seen from these figures above, there is a correlation between the integrating ice index and the freight cost. As for 40BC, approximately 50% of the calculated freight costs is lower than the freight cost of through the SUEZ route, which is 39.7$/ton, as Figure 4.1.19 shows. The ideal condition of the use of NSR seems to be a year round basis. However, considering the effective use of the NSR, the SUEZ route should be used during the severe cold seasons when the freight cost is more expensive. Therefore, the route at the annual voyage simulation is assumed to switch between the NSR and the SUEZ judging the ice condition. The cumulative ice index along the route was adopted as the criterion of switching. The critical cumulative ice index for switching is decided from the value corresponding to the freight cost of the SUEZ route. From the results of Figure 4.1.19 and 4.1.20, the critical values of -26000 for 40BC and -50100 for 50BC were adopted respectively.
