Since 1996, a Brazilian railway concessionary has been responsible for an extensive transportation network including 631 bridges and viaducts, located in the most economically prominent states located in Southeastern Brazil. To guarantee railway bridges performance, an instrumentation program was adopted with the objective of getting a better knowledge of the structural performance and estimating remaining fatigue life of the bridges. Since 2015 monitoring tests were accomplished during normal railway operation. In some cases, instrumented trains were used as excitation force to the structure. Measured bridge dynamic responses have been used to evaluate the quality and the structural integrity of the bridges along the railway. With this aim a hybrid analysis using data from monitoring and from finite element models was accomplished. This procedure was applied to identify 50 bridges in the railway operated by the concessionary. Recently Brazilian Standard NBR-7189 which refers to railway loads to be considered in the design of bridge structures, was updated. In the process, some values measured in railway bridges operated by the Brazilian railway concessionary were considered to calibrate expressions proposed for the impact factors, breaking and acceleration forces. For example, measured dynamic amplification factors were compared with values calculated using impact formulation, giving an idea of whether the formulation is adequate. Horizontal forces measured in elastomeric bearing were compared with forces of breaking and acceleration, and a suitable percentage of the live load was determined to represent the longitudinal forces due to train passages. Besides that, other formulations that are dependent of dynamic properties of bridges were updated considering empirical curves based on measured values, like for example curves of natural frequency and bridges spans.