Rail expansion device and method

The present invention concerns a rail expansion device (30) and a method for compensating an expansion of a first rail (F1) with respect to a second rail (R2), the rail expansion device (3) being configured for joining the first rail (F1) to the second rail (R2) and comprising: - a front connecting rail (31), comprising a front end FE1 and a rear end RE1 (RE1), wherein the front end FE1 is configured for being connected to the first rail (F1); - a rear connecting rail (32) comprising a front end FE2 (FE2) and a rear end RE2 (RE2), wherein the rear end RE2 (RE2) is configured for being connected to the second rail (F2); characterized in that the rail expansion device (30) comprises a splice joint configured for slidably connecting the rear end RE1 (RE1) to the front end FE2 (FE2), said splice joint defining a continuous running surface (RS) from the front connecting rail (31) to the rear connecting rail (32), wherein said continuous running surface (RS) is characterized by a variable longitudinal length config