  In this article, we study transportation network in Minnesota. We show that
the system is characterized by Taylor's power law for fluctuation scaling with
nontrivial values of the scaling exponent. We also show that the characteristic
exponent does not unequivocally characterize a given road network, as it may
differ within the same network if one takes into account location of
observation points, season, period of day, or traffic intensity. The results
are set against Taylor's fluctuation scaling in the Nagel-Schreckenberg
cellular automaton model for traffic. It is shown that Taylor's law may serve,
beside the fundamental diagram, as an indicator of different traffic phases
(free flow, traffic jam etc.).
