Recommendations are given for the vehicle characteristics to be used in the assessment of the fatigue life of bridges and other structures subject to traffic loading. They are based on an examination of vehicle loading and observations of the pattern of traffic flow on major roads. The aim is to provide a consistent basis for comparison of different designs and to enable the fatigue life to be estimated.nThe vehicle characteristics include axle configurations and loads, details of wheel units, and tyre contact areas. For the purpose of design calculations an estimation is made of the number of normal commercial vehicles per day for the left-hand lane of a major road; numbers are given for vehicles in the middle lane of a three-lane carriageway and for coincidence of vehicles in adjacent lanes. The numbers and weights of vehicles carrying abnormal loads are also considered.nA method of using the data for estimating fatigue life is outlined, and an example is given of the application of the fatigue data of BS 153 to a welded steel stringer. The effects on fatigue life of HA and HB design loading, and changes in the dead/live load ratio, design stress and class of weld are indicated.
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