Because of explicit restrictions imposed by the journal, it is
unfortunately not possible to keep the preprint here.  Please contact
kai at inf dot ethz dot ch for further information.

Here is at least the abstract:

Certain aspects of traffic flow measurements imply the existence of a
phase transition. Models known from chaos and fractals, such as
non-linear analysis of coupled differential equations, cellular
automata, or coupled maps, can generate behavior which indeed
resembles a phase transition in the flow behavior. Other measurements
point out that the same behavior could be generated by 
geometrical constraints of the scenario. This paper looks at
some of the empirical evidence, but mostly focuses on different
modeling approaches.  The theory of traffic jam dynamics is reviewed
in some detail, starting from the well-established theory of kinematic
waves and then veering into the area of phase transitions.  One aspect
of the theory of phase transitions is that, by changing one single
parameter, a system can be moved from displaying a phase transition to
not displaying a phase transition.  This implies that models for
traffic can be tuned so that they display a phase transition or not.

The paper focuses on microscopic modeling, i.e.\ coupled differential
equations, cellular automata, and coupled maps.  The phase transition
behavior of these models, as far as it is known, is discussed.
Similarly, fluid-dynamical models for the same questions are
considered.  A large portion of the paper is given to the discussion
of extensions and open questions, which makes clear that the question
of traffic jam dynamics is, albeit important, only a small part of an
interesting and vibrant field.  As our outlook shows, the whole field
is moving away from a rather static view of traffic toward a dynamic
view, which uses simulation as an important tool.