What is the test for res ipsa loquitur in a motor vehicle accident?

The plaintiff's argument with respect to Selander is that he was unable to give a satisfactory explanation for driving off the road and, therefore, negligence may be assumed against him. The only unexplained part of the accident here is how the truck crane happened to slip off the road and it was acknowledged by counsel that this could happen without negligence. The movements from that point on are fully explained by Selander. The learned trial Judge held that he could not say that the accident was one which in the ordinary course of things would not have happened if Selander had used proper care. The vehicle was on a road that was described as rolling. The machine had a boom sticking over the front which made the vehicle more difficult to control. Selander had 22 years of experience in driving heavy equipment and the learned trial Judge referred to him as "an honest witness" and obviously accepted his evidence. He also referred to the fact that the front spring hanger had broken and said it could be inferred that this had broken prior to the accident and this had caused the vehicle to go off the paved surface, although Selander said he had no indication prior to the accident that this had happened. Under all of the facts here, I am in respectful agreement with the finding of the learned trial Judge that res ipsa loquitur did not apply: see McKay v. Gilchrist et al. (1962), 1962 CanLII 286 (SK CA), 35 D.L.R. (2d) 568, 40 W.W.R. 22.