TRAFFIC jams are a fact of life for many car drivers. Every morning millions of drivers around the world sit motionless in their vehicles for long periods of time as they try to get to work, and then repeat the experience on their journeys home in the evening. The same thing often happens when they are driving to the coast for the weekend or to the airport to go on their holidays. They blame other drivers, increasing volumes of traffic and, inevitably, roadworks. So what has any of this got to do with physics?
Well, consider every car as an "elementary particle" that is constrained to move along a one-dimensional trajectory. This particle must also obey certain conditions: for example it must try to get from A to B and it must not collide with other particles! Could the collective behaviour of this complex system be responsible for traffic jams and the various other features associated with traffic flow? Does this behaviour have anything in common with the phenomena of self-organization and pattern formation that have been discovered in recent years? Indeed, should traffic phenomena be considered as part of statistical or nonlinear physics?
In the August issue of Physics World magazine, Boris Kerner of DaimlerChrysler AG in Germany writes about the physics of traffic.
Further reading
M Bando et al. 1995 Phenomenological study of dynamical model of traffic flow J. Phys. I France 5 1389 R Barlovic et al. 1998 Metastable states in cellular automata for traffic flow Eur. Phys. J. B5 793 D Helbing and M Schreckenberg 1999 Cellular automata simulating experimental properties of traffic flow Phys. Rev. E59 R2505 B S Kerner 1998 Experimental features of self-organization in traffic flow Phys. Rev. Lett. 81 3797 B S Kerner 1999 Congested traffic flow: observations and theory Transportation Research Record at press; preprint no. 990106 Transportation Research Board, 78th Annual Meeting, January 1014 (TRB, Washington, DC) B S Kerner and P Konhäuser 1994 Structure and parameters of clusters in traffic flow Phys. Rev. E50 54 B S Kerner and H Rehborn 1996 Experimental features and characteristics of traffic jams Phys. Rev. E53 R1297 B S Kerner and H Rehborn 1996 Experimental properties of complexity in traffic flow Phys. Rev. E53 R4275 B S Kerner and H Rehborn 1997 Experimental properties of phase transitions in traffic flow Phys. Rev. Lett. 79 4030 S Krauß et al. 1997 Metastable states in a microscopic model of traffic flow Phys. Rev. E55 5597 H Y Lee et al. 1999 Dynamic states of a continuum traffic equation with on-ramp Phys. Rev. E59 5101 R Mahnke and J Kaupuzs 1999 Stochastic theory of freeway traffic Phys. Rev. E59 117 A D May 1990 Traffic Flow Fundamentals (Prentice-Hall, New Jersey) M Treiber et al. 1999 Derivation, properties, and simulation of a gas-kinetic-based, nonlocal traffic model Phys. Rev. E59 239
