The composite steel-concrete bridge across the “Slavičí údolí” on the Prague ring exposed to extreme traffic is selected for present traffic flow monitoring. The response of the bridge to the traffic loads is monitored using strain gauges. The record of voltage is converted to the amount of relative deformation, respectively stress in the bottom flange of steel I beam of the bridge. In parallel with the measurements, the computer slab - wall model based on finite element method is developed. The computer model is used for comparison of calculated and measured stresses and deflections in the flanges and to determine the natural frequencies of the examined bridge structure. Calibrated measurements are used for three-year monitoring of the effects of road traffic on bridge facilitating national decision in the National Annex to EN 1991-2.