Density Fluctuations in Traffic Flow
  Density fluctuations in traffic current are studied by computer simulations using the deterministic coupled map lattice model on a closed single-lane circuit. By calculating a power spectral density of temporal density fluctuations at a local section, we find a power-law behavior, $\sim 1/f^{1.8}$, on the frequency $f$, in non-congested flow phase. The distribution of the headway distance $h$ also shows the power law like $\sim 1/h^{3.0} $ at the same time. The power law fluctuations are destroyed by the occurence of the traffic jam. 
S. Yukawa and M. Kikuchi