Yūki Sugiyama

Power-Law Fluctuation in Expressway Traffic Flow: Detrended Fluctuation Analysis

The temporal behavior of expressway traffic flow is a complex mixture of various time scales. The fundamental response time of drivers is on the order of 1 s, and the periodic appearances of traffi...

Analysis of congested flow at the upper stream of a tunnel

We analyze the traffic data observed at the upper stream of a tunnel (Nihonzaka Tunnel) on Tomei Expressway linking Nagoya with Tokyo. We observe the fundamental properties of the traffic flow including temporal sequences and statistical properties. We also observe the reverse-lane usage in which the flow on the fast lane exceeds the one on the slow lane.

Instability of pedestrian flow in 2D optimal velocity model with attractive interaction

We incorporate an attractive interaction in two-dimensional optimal velocity model and investigate the stability of homogeneous flow. There exists a new type of instability and a new phase appears. We also show the behavior of the flow in each phase by numerical simulations.

Optimal velocity model for traffic flow

We present the Optimal Velocity (OV) model for traffic flow, which shows spontaneous formation of a jam cluster. We investigate the phase diagram and the general bound of induced time delay which plays an essential role in the jam flow solution.

Observation, Theory and Experiment for Freeway Traffic as Physics of Many-Body System

The importance of physical viewpoint for understanding the phenomena of freeway traffic is emphasized using the simulations of a mathematical model and the experiment. The traffic flow is understood as a many-body system of moving particles with the asymmetric interaction and the emergence of jam is the pattern formation as the phase transition of non-equilibrium system by the effect of collective motions.

Meanfield Study of Radially Active U(1) and SU(2) Higgs Model

The phase structure of lattice Higgs model has been studied by many authorsl)-4) with radial excitations of the Higgs scalar frozen out. Revealed was a remarkable feature of complementarityl),5) which states that, in Higgs models with a scalar in the fundamental representation, the Higgs and the confining phases are analytically connected with each other. Many applications of the complementarity have been made in the continuum theory.6) However the continuum limit of lattice models is expected to be attained for renormalizable interactions,7) whereas the frozen Higgs models are not renormalizable. It will thus be necessary to study radially active models and clarify their phase structures. Many approaches are possible; Monte Carlo simulations and analytic studies. Among the latters the meanfield (MF) theory is very useful since it has succeeded in reproducing phase diagrams qualitatively and enables us to calculate further corrections systematically.3) Recently Munehisa and Munehisa) have performed a Monte Carlo study of a radially active Z2 lattice Higgs model using a discrete approximation of the radial mode r. In the previous paper) we made a series of MF studies of this model and showed that the MF theory was qualitatively successful also in the radially active model as in the frozen model. 4) We also discussed that the concept of a mode correlation is useful to understand the physical properties of each MF model. In this paper we extend the previous analysis to more realistic Higgs models of U(1) and SU(2) gauge groups. In §2 we first introduce the models and give a brief review of MF method in a suitable manner for application to our models. We then investigate the U(1) and SU(2) Higgs models in §§3 and 4. Section 5 is devoted to the conclusion and discussion.

Optimal Velocity Model and its Applications

We review some aspects of the optimal velocity (OV) model and compare these aspects with those of other car-following models. We also show two applications of the OV model. One is an application to the intelligent transport system, especially how to suppress the emergence of traffic congestion. The other is an application to pedestrian flow. For these purposes, we propose some extensions of the OV model.

Long-Term Traffic Data from Japanese Expressway

Recent development of physics-based mathematical modelling of highway traffic has brought us to a new stage of research. For example, reproduction of overall shape of the q-k diagram, which itself has once been a big challenge, is now one of the least requirements that any good model should achieve. The interest for physicists has been shifted to deeper understanding of traffic behavior such as details of the instability near the capacity and spatio-temporal structures of traffic jams Understanding them is, without doubt, important also for traffic controls in future.

Dynamics of Dissipative System with Asymmetric Interaction and N-Body Problem for the Emergence of Moving Cluster

Collective motion of self-driven particles is a non-equilibrium dissipative system with asymmetric interaction. Optimal Velocity Model is a minimal model formulated with Newtonian equation of particles in nonlinear asymmetric interaction with dissipative (viscous) term. Through the investigations of OV model we show the general properties in such systems: The inseparable relation between the asymmetry and dissipation. The particle-number N (or density) is a control parameter for the instability of a system. The small-N is large enough degree of freedom in such many-particle systems. They contrast sharply with the energy-momentum conserved systems.

Fluctuation in Expressway Traffic Flow

The temporal data of the expressway traffic data are complex mixtures of various time scales. The periodic appearances of the congestion, for example, reflect social activities. We need some filters to extract proper fluctuations from the raw data. We employ the method of detrended fluctuation analysis for studying the time sequence of the traffic flow. We find the long-range correlation from 1 hour to 24 hours.