  A dynamical system is considered such that, in this system, particles move on
a toroidal lattice of the dimension $N_1\times N_2$ according to a version of
the rule of particle movement in Biham--Middleton--Levine traffic model.
Particles of the first type move along rows, and the particles of the second
type move along columns. A particle can change its type. The probability that,
at a step, a particle changes the type equals $q.$ It has been proved that, if
whether $q>0$ or $q=0$ and there are at least one particle of the first type
and there is at least one particle of the second type, then a necessary
condition for a state of free movement to exist is that the greatest divisor of
$N_1$ and $N_2$ be not less than~3. The system is represented as an algebraic
structure over a set of matrices corresponding to states of the system. The
theorems are formulated in terms of the algebraic structures and terms of the
dynamical systems. The model is also presented as a Buslaev net. The spectrum
of the net $2\times 2$ has been found.
