What is the test to establish causation in a motor vehicle accident?

The appellant cited Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458 at 466, that sets out the tests to establish causation. Stated briefly, causation is established where a plaintiff proves that a defendant caused or contributed to an injury and where a plaintiff shows that the injury would not have happened but for the negligence of the defendant. Where the “but for” test is not workable, a plaintiff may establish causation by proving that the negligence materially contributed to the injury. A contributing factor is material if it falls outside of the de minimis range.