Exactly Solvable Single Lane Highway Traffic Model With Tollbooths
  Tolls are collected on many highways as a means of traffic control and revenue generation. However, the presence of tollbooths on highway surely slows down traffic flow. Here, we investigate how the presence of tollbooths affect the average car speed using a simple-minded single lane deterministic discrete traffic model. More importantly, the model is exactly solvable. 
H. F. Chau, H. Xu and L.-G. Liu