Prestressed concrete ties offer an alternative to the timber ties which are used presently on North American open deck railway bridges. This paper presents the results of a field study of an open deck railway bridge equipped with precast prestressed concrete ties subjected to a special work train and regular railway traffic. The results of the study show that a train with smooth wheels does not overload the bridge deck. When wheel defects are present, the bridge deck loading is speed-dependent and consists of distinct static and dynamic components. Test results show that the tie design loads are underestimated. The impact on the bridge deck due to the defective wheels was also found not to amplify the response of the bridge longitudinal steel girders.Key words: bearing pads, impact load, railway bridge, load distribution, dynamic load factor, open deck, precast prestressed concrete, ties, wheels.