  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.
