  This paper is an extended abstract on a traffic model for the train dynamics
on a metro line with a junction. The dynamic model includes control laws on the
dwell and on the run time, taking into account the passenger travel demand. Our
model extends two existing traffic models: 1. a model that describes the train
dynamics on a metro line with a junction but without taking into account the
travel demand, i.e. dwell and run times are fixed, and 2. another model that
controls the train dynamics on a linear metro line (without junction) taking
into account the passenger travel demand. We present the phase diagram of the
train dynamics in the metro line with a junction. Train time-headway and
frequency are functions of 1. the number of trains on the line, 2. the
difference between the number of trains on the two branches, and 3. the
passenger demand level. The derived diagram can be used for the optimization of
the traffic control on the metro line and at the junction.
