It is not possible to use these two latter ship types for comparisons with cargo ships, since they operate under very different conditions.
Akukwazeki ukusebenzisa olu hlobo lwezinqanawa zimbini zichazwe mva ekuthelekiseni kunye neenqanawa zokuthutha imithwalo, ngenxa yokuba zisebenza phantsi kwemeko ezahlukeneyo kakhulu.