Long-haul passenger, commuter, and freight railroads are essential to maintaining a thriving economy and environmentally friendly, efficient and less congested transportation system for people and goods, especially in New England, with its many urban areas, industries, and major national defense activities. On Amtrak’s Northeast Corridor between Washington, D.C. and Boston, MA, the busiest passenger rail corridor in the United Sates, there are over 60 long span steel bridges that are more than 100 years old. This situation presents many structural problems, especially overstress in certain members, as well as fatigue. This research focused primarily on two areas. First, developing a finite element (FE) model that can reliably predict the impact, as derived from other bridge responses (displacement and strain), for trains at speeds higher than that currently allowed on these structures. And second, field research to accumulate data on bridge response from each of the train types at various speeds. The research used as test vehicles, two types of Amtrak train sets, Acela higher speed vehicles, and Amtrak conventional Regional train vehicles, as well as Metro-North Railroad’s M8 MU commuter cars. Specific to this research is the type of bridge structure. The model was based on an open deck, long span through truss. This type of bridge is typical of hundreds still in service around the country, and most appreciably over a hundred years old, especially in the Northeast. Field research was conducted on Devon Bridge, a 115-year-old bridge, opened in 1906, over the Housatonic River between Stratford and Milford, Connecticut, and owned by the Connecticut Department of Transportation. The model was developed using STAAD.Pro software. Using the known physical characteristics (axle loads and axle spacing) of the Amtrak and Metro-North vehicles, field tests verified high correlation between actual bridge responses, measured by displacements and strains at various speeds, and those predicted by the model. Thus, the model can be useful in predicting impact values, derived from displacements and strains, from similar types of vehicles on this and other open deck railroad bridges. Additional study and analysis were performed on bridge response under live load to better understand how the relative old age of the test structure, and its long history from use by steam engines and heavy freight trains, effect certain truss members’ response. Particular investigation was performed on the eyebars, which are used as counter diagonals and lower chord members in the truss. Results from this investigation were compared to tests performed several years earlier, and analysis is presented for why some differences appear. A thorough review was also performed contrasting railroad bridges design impact requirements used in countries around the world. The knowledge gained from this research can be applied to other railroad bridges of this type, carrying comparable conventional passenger cars and MU transit cars.