This report is one of a series that describe the TRRL contribution to a joint european research project to study traffic loads and stresses in steel bridges, and it discusses traffic load data obtained at three bridges. The axle load data are more detailed than are normally available, for instance front and rear axles are considered separately because front axles are shown to make a significantly greater contribution to potential fatigue damage than previously thought. A curve fitting procedure for the front and rear axle load spectra is adopted. A method of defining the fatigue damaging potential of an axle load spectrum is described; it has been called the characteristic axle load of the spectrum. Axle load data by vehicle class are given for two bridges; the 2-axled rigid is the most common commercial vehicle, followed by the 4-axled articulated. In terms of fatigue damaging potential however the 4-axled articulated is worst. Characteristic axle loads are given for the overall axle load spectra for the eleven bridges in the joint project; the british bridges have the lowest values. A value is also given for one of the most heavily trafficked roads in britain to provide an 'upper bound' estimate for british traffic. A comparison of the frequency of occurrence of the vehicle classes is also given for the eleven bridges.

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