Dresden 2009 – scientific programme

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AGSOE: Arbeitsgruppe Physik sozio-ökonomischer Systeme

AGSOE 8: Traffic Dynamics, Urban and Regional Systems II

AGSOE 8.2: Talk

Tuesday, March 24, 2009, 10:45–11:15, BAR 205

Comparing fluctuations in traffic flow with thermal noise in physical pattern forming systems — •Martin Treiber — TU Dresden, Dresden, Germany

Thermal noise in physical pattern-forming fluid systems (such as Rayleigh-Benard convection or Taylor-Couette flow) increases in a characteristic way when approaching a linear stability threshold from below. This can be described quantitatively by generalizing the fluctuation-dissipation theorem to nonequilibrium systems.

In this contribution, I show that the same is true when (non-thermal) noise is applied to pattern-forming systems driven by nonphysical forces, with traffic flow being a prominent example. Sufficiently far away from threshold, many concepts of equilibrium thermodynamics carry over to the traffic system although neither energy nor momentum are conserved. Particularly, the fluctuations allow to determine a generalized "interaction potential" from the data.

Simulations show that, when approaching the linear stability, the fluctuations increase in the traffic system as well. Moreover, correlations appear that anticipate, in a way, the patterns of stop-and go traffic observed once above threshold. Both results could be described nearly quantitatively by analytical methods that have been successfully applied to the thermal fluctuations of the physical pattern-forming systems.