Plaintiff\u27s empty truck, proceeding uphill, collided on plaintiff\u27s side of the road with defendant\u27s loaded truck which was traveling in the opposite direction. Both trucks were engaged in the same road-surfacing project. The road had a washout on defendant\u27s side. Defendant\u27s answer alleged that there was an established custom under which drivers of empty trucks yielded the right of way to drivers of loaded trucks when about to meet in a narrow or defective place in the highway; that defendant relied upon such custom which plaintiff failed to observe; and that the plaintiff\u27s failure to observe the custom constituted contributory negligence. The trial court granted the plaintiff\u27s motion to strike these allegations on...