If a person breaches this duty and damages occur as a causation of the breach a person is liable. The damages may occur from the actual causation of the breach or a proximate causation of the breach if the causation is foreseeable.
Analysis: Brian swerved into the gutter to avoid hitting the cat that ran into the street. By running into the gutter he caused a board to break that then hit Susan in the head causing her to lose conscious. Susan then runs off the road and hits Little Johnny causing serious injury.
Conclusion: If Brian was not speeding and as the cat ran into the street, so it was not a case of not paying attention, I would argue that Brian acted as a reasonably prudent person by swerving into the gutter and therefore did not breach duty. I would also argue that it was an unforeseeable event that a piece of wood would be in the gutter and break causing a passing motorist a concussion. Brian is not liable under the tort theory of negligence to Susan and Little Johnny. Susan was unconscious and did not breach duty so she is not liable for the injuries to Little