Universal behaviors in granular flows and traffic flows

We review the current understanding on universal behaviors in granular flows through a vertical pipe and traffic flows. We carry out weakly nonlinear analysis of a model for traffic flows based on the technique of soliton perturbations, and determine the selected propagating velocity, the amplitude, the width of interfaces connecting between jam phase and non-jam phase. From the direct simulation of the model, we have confirmed the validity of our theoretical analysis. We also introduce a model for granular pipe flow supplemented by the white noise, which reproduces $P(f)\sim f^{-4/3}$, where $P(f)$ is the power spectrum in the frequency $f$.