Traffic loads are the major cause of fatigue cracks in steel bridges.A rational traffic load model is indispensable for bridge design and assessment.Presently,several countries had developed their own traffic load models for fatigue design and assessment based on nationwide traffic survey (BSI,1980; Japan Road Association,2002; AASHTO,2004).Two points were to be declared herein.1) Traffic load models for fatigue design and assessment were different from those for load capacity design and assessment.It should reflect the operational condition of traffic loads other than extreme events that induced most adverse effect; 2) Traffic load models for design purpose may not appropriate to assessment.