The problem of train passage over bridges is an interaction problem between two systems; the bridge system including track and the passing train system. To consider the bridge-vehicle interaction, a non-linear problem shall be solved, because the response of each system depends on the response of the other system simultaneously. Two ways of solving the interaction problem are applied in an FE numerical domain, where the first way treats the two systems as one whole system, which dynamically updates its stiffness matrix, while the second way considers the transferred forces at contact points between two decoupled systems with constraint equations. The bridge system is modeled as 2D Bernoulli beams and the track as a single continuous non-viscous elastic layer beneath rails with irregularities, whereas the train system is modeled as separate moving systems with each system having two degrees of freedom (DOFs) and consisting of a lumped mass supported by one layer of suspension system that comprises a spring-damper unit. The parametric study on a non-prismatic continuous prestressed concrete bridge using a high-speed train shows that the interaction models give similar responses to moving-load model except at resonance speeds for which conservative values and higher resonance speeds are given.