What is the current state of the law on sudden stops?

[22] The trial judge correctly identified the central issue of the trial when she said, “The question then is whether or not the sudden stop of the bus was negligent.” She found that the stopping created a prima facie evidentiary case of negligence, but that there might be a good reason for stopping which would mean it was not negligent. She rejected the application of the series of authorities starting with Day v. Toronto Transportation Commission.