What is the defence of negligence in a motor vehicle accident?

10 To establish the defence, the defendant must show such circumstances to exist that ... it is clear that the plaintiff, knowing of the virtually certain risk of harm, in essence bargained away his right to sue for injuries incurred as a result of any negligence on the defendant's part. The acceptance of the risk may be express or may arise by necessary implication from the conduct of the parties, but it will arise ... only where there can truly be said to be an understanding on the part of both parties that the defendant assumed no responsibility to take due care for the safety of the plaintiff, and that the plaintiff did not expect him to. Dube v. Labar, 1986 CanLII 67 (SCC), [1986] 1 S.C.R. 649, per Estey J.

11 In Hall v. Hebert, 1993 CanLII 141 (SCC), [1993] 2 S.C.R. 159 (at 208) Cory J. put it in this way: The doctrine [volenti] will only be applied where it can truly be said that there is an understanding on the part of both parties that the defendant assumed no responsibility to take care for the safety of the plaintiff and the plaintiff did not expect him or her to do so. Clearly, the volenti defence will only be applicable in a narrow range of cases. (my emphasis)