“…Such a phenomenon is intrinsic to first-order quasilinear partial differential equations (FOQLPDEs), including the kinematic wave model, the Kynch's sedimentation model (Bürger and Wendland, 2001), the compressible Euler equations (Chen et al, 2017), and traffic flow models (Corli and Malaguti, 2021). Conversely, treatment of the kinematic wave model not as a FOQLPDE but a Hamilton-Jacobi type leads to inconsistency as in Mean et al (2020). Those properties are well-known among mathematicians since Oleĭnik (1957) established the theory of FOQLPDEs in 1D domains, considering generalized solutions in the space of measurable and bounded functions.…”