A rail expansion device compensates for an expansion of a first rail with respect to a second rail. The rail expansion device joins the first rail to the second rail. The expansion device has a front connecting rail, containing a front end and a rear end, wherein the front end is configured for connecting to the first rail. A rear connecting rail, has a front end and a rear end, wherein the rear end is configured for connecting to the second rail. A splice joint is provided and configured for slidably connecting the rear end to the front end. The splice joint defines a continuous running surface from the front connecting rail to the rear connecting rail, wherein the continuous running surface has a variable longitudinal length configured for varying in function of a width of an expansion gap separating the front connecting rail from the rear connecting rail.