What is the relation-back doctrine in motor vehicle accident law?

by the doctrine is that "[a]n amended complaint relates back to the original complaint, and thus avoids the statute of limitations as a bar against named parties substituted for fictitious defendants, if it: (1) rests on the same general set of facts as the original complaint; and (2) refers to the same accident and same injuries as the original complaint." (Id. at p. 151.) The relation-back doctrine can also be applied when an amended complaint alleges additional causes of action against the same defendants, as long as they arise from the same facts alleged in the original complaint. (Dudley v. Department of Transportation (2001) 90 Cal.App.4th 255, 266.)