Dynamics of railway bridges is a complicated problem that normally needs nu- merical simulation to conduct researches on. However, this thesis takes advan- tage of the numerical results provided in previous researches and based on these researches, further conclusions are made by using them in simplified model. Recently long span railway bridges being designed in the Netherlands are being rejected by a particular Eurocode criterion that requires bridges to possess a first lateral natural frequency higher than 1.2Hz. Due to the fact that generally bridge’s first lateral natural frequency decreases as the span increases, it can be seen that 1.2Hz criterion is rejecting almost all bridge with a span longer than 150m. This report succeeds in pursuing the original documents of 1.2Hz criterion and the knowledge in the documents initiates further researches on the lateral dy- namics of railway bridges. Besides 1.2Hz criterion itself, following topics are researched with the information provided by previous researches: 1. Train-bridge lateral resonance mechanisms, including axle repeat pattern resonance and kinematic movement resonance, 2. Lateral force on tracks caused by the operation of railway vehicle and key parameters influencing the force. Taking advantage of the items above, a simplified model for checking the lateral railway bridge dynamics is developed to quantify the lateral dynamic resonance response of railway bridge under horizontal dynamic vehicle load. This method aims to serve for engineering purposes and provide an alternative way of ver- ifying railway bridge lateral dynamics. The practical method is developed by an analytical approach, based on the numerical simulation results provided by other researches. An illustration of the usage of the practical method is conducted on the basis of a real bridge project. The method is also implemented in Matlab scripts to automate the checking procedure.