2020 年 40 巻 2 号 p. 26-43
Threats of potential natural disasters have necessitated the urgency to construct and sustain a highly reliable network for promotion of national resilience. However, improving all the links simultaneously is difficult due to budget constraints. Therefore, network reliability can be improved effectively by improving the most important key link. Our previous research revealed that improved criticality importance(CIW) is better than reliability importance (RI). However, as link reliability increases, the difference between the values of both indicators shrinks in terms of fairness of link improvement. In this study, we compared four importance indices. The newly added indices are Fussell-Vesely (FV) and the risk achievement worth (RAW), which are used in highly reliable systems (e.g., nuclear power plants). CIW, RI, FV, and RAW are compared by terminal reliability, difference between maximum and minimum values of link reliability (DBMM), and number of improved links. First, RI and RAW improve terminal reliability better compared with CIW and FV; however, the difference is small. RI and RAW give a larger DBMM than CIW, which indicates that using RI implies more gaps between parallel routes than using CIW and FV. Moreover, CIW is the best in terms of fairness of link improvement, as it has the largest number of improved links. Therefore, CIWis a recommended importance index.