P testified that he was injured on a D bus. He had entered the bus and was climbing the stairs to the platform on which the seats were located. Before reaching the platform, the bus pulled out and stopped suddenly. The doors to the bus had not closed at the time of the accident, and he injured his arm. D claimed that the accident never occurred and if it did there was no negligence on the part of D's driver. The court instructed the jury on ordinary negligence. D got the verdict and P appealed.