The traffic congestion often occurs in urban road
network. When one of the sections becomes congested, it will lead
to a series of congestions in other sections. The traffic
congestion spreads rapidly until part of road network becomes
congestion ultimately. In this case, the paper investigates the
mechanism of the traffic congestion in urban road network and
points out that subsystems of the traffic congestion always
perform completive and cooperative functions in the process of
traffic congestion. The process behaves in a manner of
self-organized criticality, which can be forecasted. The paper
also establishes synergetic predictive models based on
self-organized criticality of the synergetic theory. Finally, the
paper takes Beijing road network as an example to forecast the
widespread traffic congestion. The result shows that the
established models are accuracy, and the traffic congestion
is featured of self-organized criticality.