On the equivalence between continuum and car-following models of traffic flow
For traffic flow modelers, this provides a unified framework to translate between two modeling paradigms, enabling cross-fertilization and consistency checks.
The paper proposes a systematic method to convert between higher-order continuum and car-following traffic flow models, revealing that they share the same fundamental diagram but have different stability conditions. The method generates new models and clarifies relationships among existing ones.
Recently different formulations of the first-order Lighthill-Whitham-Richards (LWR) model have been identified in different coordinates and state variables. However, there exists no systematic method to convert higher-order continuum models into car-following models and vice versa. In this study we propose a simple method to enable systematic conversions between higher-order continuum and car-following models in two steps: equivalent transformations of variables between Eulerian and Lagrangian coordinates, and finite difference approximations of first-order derivatives in Lagrangian coordinates. With the method, we derive higher-order continuum models from a number of well-known car-following models. We also derive car-following models from higher-order continuum models. For general second-order models, we demonstrate that the car-following and continuum formulations share the same fundamental diagram, but the string stability condition of a car-following model is different from the linear stability condition of a continuum model. This study reveals relationships between many existing models and also leads to a number of new models.