“…As to model identification, which is another feature of PIDL-based TSE, this paper only assumes a traffic flow conservation equation and optionally, a momentum equation for the velocity field, without specifying any mathematical relation between traffic quantities. The aforementioned related studies in [39], [41] directly fit a velocity function using measured density and velocity from probe vehicles before or during the PIDL training. In contrast, we focus on a more general case, where the output of the FD function is unobserved from sensors, and the end-to-end FD relation is to be learned directly using ML surrogates under the PIDL framework.…”