Abstract:Abstract : Research purposes : Taking Shanghai - Nantong super - long - span (142 + 462 + 1092 + 462 + 142) m highway and railway cable - stayed bridge as an engineering background, the additional deformation induced by the upper highway live load and temperature effect was considered in the analysis of process of train - track - bridge coupling system to assess the impact to performance of running train. By comparing the vehicle bridge dynamic response indexes under tlie condition of various additional deformation,the impact to traffic performance was evaluated. Research conclusions :( 1) Transverse displacement of the bridge under the additional deformation induced by live loads of highway was almost unchanged, as it increased from 6. 453 mm to 7. 332 mm under the additional deformation of temperature difference,rising by about 14;. (2) Vertical displacement of the bridge under various additional deformation has almost no change. ( 3 ) When considering various kinds of additional deformation, the derailment coefficient,the wheel unloading rate,the vertical and lateral acceleration and riding index of tlie driving train had barely changed,but under the effect of 10 E temperature difference,the wheel/rail force increased form 18. 552 kN to 19. 371 kN. (4) The researdi results could provide references for engineering design of super - long - span highway - railway cable - stayed bridge.