What is the test for determining whether there was a but for causation in a motor vehicle accident?

As Justice Sopinka said in Snell v. Farrell, [1900] 2 S.C.R. 311: “causation is essentially a practical question of fact which can best be answered by ordinary common sense.” The language that the trial judge used in making her findings on causation show that she indeed applied the “but for” test. Her findings are supported by the record. Moreover, her findings reflect the common sense proposition that but for the City’s breach of the standard of care, this accident would not have happened.