Starting from a continuous follow-the-leader model for individual vehicle motion a stochastic term is added in order to account for the elementary randomness of driving. In a suitably defined stationary state thus an equilibrium distribution of nearest-neighbour distances is spanned up which allows to understand the “fundamental diagram” of macroscopic traffic flow modelling as the ensemble average of the microscopic characteristic function. Estimates for the distribution width and a comparison with simulation results are given.