What is the test for liability in a motor vehicle accident?

As Howden J. wrote in Deering v. Scugog (Township), 2010 ONSC 5502, 3 M.V.R. (6th) 33, affirmed 2012 ONCA 386, leave to appeal to S.C.C. refused [2012] S.C.C.A. No. 351, at para. 100: [t]he principle that the standard of care to be met by road authorities is not perfection. Further, it is neither determinative of liability that an accident occurred on the road in question, nor is it sufficient for a claimant to show that the road could have been made safer by some improvement, pavement marking or other means where cues that should be reasonably obvious to the ordinary driver called for caution. The question remained in all such cases: was the road at the material time sufficiently in repair that those users of the road, exercising ordinary or reasonable care, could use it in safety?