With the increasing volume of freight traffic and the growing emphasis on structural monitoring of existing bridges, it is essential to apply operational modal analysis to identify the intensity and frequency of vehicle crossings. In this paper it is proposed a multi-parameter identification method that estimates the intensity, and spacing of moving loads on a beam bridge. The method is derived from a comparison between a one-dimensional analytical model and in-situ structural responses. In detail, to model the bridge dynamics, a coupled flexural-torsional Euler-Bernoulli beam model is used, accounting for bridge skeness and moving loads with varying intensities and non-uniform spacing. The identification process is carried out using the Differential Evolution genetic algorithm.