A state statute requires motorcyclists to wear a safety helmet while riding, and is enforced by means of citations and fines. Having lost his helmet, Adam jumped on his motorcycle without one and went riding down the street. Barb, who was driving her car in the opposite direction on the same street, briefly looked down to get her sunglasses, which had dropped to the floor. At that moment, a bee landed on Adam's head. In attempting to brush it away, he lost control of the motorcycle. The motorcycle fell and went sliding over the double line into Barb's lane with Adam pinned beneath it. When Barb retrieved her sunglasses and looked ahead, she saw the motorcycle was sliding towards her, going the wrong way in the lane. She abruptly turned her wheel to avoid hitting it crossed over the double line, and collided head-on with a truck that was approaching her at twice the posted speed limit. The truck, owned and driven by Dave, was badly damaged in the collision, as was Barb's car. Barb was seriously injured when the force of the collision threw her against her own seat belt, breaking her sternum. On what theory or theories may damages be recovered, and what defenses might reasonably be raised in actions by Barb against Adam