The longitudinal movement of a structure supporting continuously welded track relative to that track results in interactive forces (interactions) being induced in both the rails and the structure. The differential movement may arise from thermal effects, volume changes in the structure, substructure deformations, or other factors. These resulting interactions are the focus of this paper.A design tool allowing the estimation of the limiting values of these interactions is presented for use by track and structure designers.The presentation begins with a discussion of the thermal stresses and movements induced in at-grade tangent continuous welded rails (CWR). The interaction of CWR and the structure is then presented, followed by a brief overview of the behaviour of CWR with rail expansion joints. The work addresses tangent tracks and will adequately apply to curved tracks with large radii, say, in excess of 500 m. Adjustments for track curvature would be required for tighter radii.Key words: trackwork, continuous welded rail, bridges, thermal stresses, force interactions.