“…Numerous mathematical models have been proposed for one-directional flows of vehicular traffic; reviews of this topic are given in the monographs by Helbing [62], Kerner [63] and Garavello and Piccoli [64], as well as in the articles by Bellomo et al [65,66,67]. These and other works vividly illustrate that the number of balance equations (for the car density, velocity, and possibly other flow variables) that form a time-dependent model based on partial differential equations, as well as the algebraic structure of these equations, is a topic of current research.…”