Bridges are lifeline structures in transportation network. Smooth flow of traffic through bridges is important consideration for socio-economic development of any regions. The bridges are generally designed with high factor of safety to cater for uncertainty in live load and material properties. With time, the structures may show various forms of degradation. This is mostly common where traffic growth is unexpectedly high and the structures are exposed to aggressive environment, which necessitates a more elaborate approach to estimate fatigue life in design phase itself. Burden of in-situ monitoring of crack growth may thus be reduced. To obtain the bridge response statistics for multiple vehicular movement which is random in nature, a semi analytical method is developed.  The time domain approach so developed has been used to simulate vehicle induced stress history and to transfer the same to fatigue damage module to obtain fatigue life of single and continuous span bridges. Different bridge vehicle parameters are taken into account to observe the effect on dynamic amplification factor and fatigue life of bridge. The developed method can be used for different vehicle models and bridge types.