I will see if I can find it, not all papers published in the 80's are online. (and I just looked the professor is emeritus at USC now but still around so I'll send him the question too)
https://www.sciencedirect.com/science/article/abs/pii/019126...!
A simplified theory of kinematic waves in highway traffic, part I: General theory
Also:
https://www.sciencedirect.com/science/article/abs/pii/019126...!
A simplified theory of kinematic waves in highway traffic, part II: Queueing at freeway bottlenecks