A quality of some fictional narrators whose word the reader can trust. There are both reliable and unreliable narrators, that is, tellers of a story who should or should not be trusted. Most narrators are reliable (Fitzgerald's Nick Carraway, Conrad's Marlow), but some are clearly not to be trusted (Poe's "Tell-Tale Heart," several novels by Nabokov). And there are some about whom readers have been unable to decide (James's governess in The Turn of the Screw, Ford's The Good Soldier).
Refers to the degree of certainty and predictability in travel times on the transportation system. Reliable transportation systems offer some assurance of attaining a given destiÂnation within a reasonable range of an expected time. An unreliable transportation system is subject to unexpected delays, increasing costs for system users
How sure you are that if someone else carried out your investigation they would get the same results and come to the same conclusions. Unreliable conclusions are worthless, other than telling you that the investigation must be modified and improved.