  An urban traffic system is a heterogeneous system, which consists of
different types of intersections and dynamics. In this paper, we focus on one
type of heterogeneous traffic network, which consists of signalized junctions
and non-signalized ones, where in the latter case vehicles usually follow the
first-in-first-out principle. We propose a novel model describing the dynamic
behaviors of such a system and validate it via simulations in VISSIM. Upon such
a new model, a signal control problem for a heterogeneous traffic network is
formulated as a mixed integer programming problem, which is solved by a
Lagrangian multiplier based hierarchical distributed approach. Comparisons
between a homogeneous traffic system and a heterogeneous one are provided,
which leaves the door open for developing a systematic planning approach on
deciding what traffic junctions require signal control to ensure a good traffic
control performance, thus, have a great social and economic potentials,
considering that it is rather expensive to have signal control in an urban
area.
