  We study the duration of "high-flow states" in freeway traffic, defined as
the time periods for which traffic flows exceed a given flow threshold. Our
empirical data are surprisingly well represented by a power law. Moreover, the
power law exponent is approximately 2, in dependently of the chosen flow
threshold. In order to explain this discovery, we investigate a simple
theoretical model of heterogeneous traffic with overtaking maneuvers, which is
able to reproduce both, the empirical power law and its exponent.
