. In view of the empty trailer, which •would have a tendency to bounce upward on a rural road, the narrow road being used as a detour, the low beam lights used in passing and Trimmer’s concession that “it did take a little longer than what I expected” to pass plaintiff’s loaded tractor trailer, the jury could have found that Trimmer’s negligent driving was the only substantial factor in causing the accident, gee Restatement of Torts (2d), § 431, comment a, p. 429, stating:

“The word ‘substantial’ is used to denote the fact that the defendant’s conduct has such an effect in producing the harm as to lead reasonable men to regard it as a cause, using that word in the popular sense, in which there always lurks the idea of responsibility, ft

*584The Pennsylvania Supreme Court has adopted such Restatement section’s view of proximate cause. See Whitner v. Von Hintz, 437 Pa. 448, 263 A.2d 889, 894 (1970).

. We note that counsel made no objections to that portion of the charge covering the issue of proximate cause. Since we have not been favored with any transcript of the summations by counsel in the above matter, it has made it difficult to determine the posture in which the case was submitted to the jury.