  We study traffic clearance distributions (i.e., the instantaneous gap between
successive vehicles) and time headway distributions by applying Beck and
Cohen's superstatistics. We model the transition from free phase to congested
phase with the increase of vehicle density as a transition from the Poisson
statistics to that of the random matrix theory. We derive an analytic
expression for the spacing distributions that interpolates from the Poisson
distribution and Wigner's surmise and apply it to the distributions of the nett
distance and time gaps among the succeeding cars at different densities of
traffic flow. The obtained distribution fits the experimental results for
single-vehicle data of the Dutch freeway A9 and the German freeway A5.
