Abstarct: Increased axial load, speed and volume of traffic on rail lines are evidence of increasing demand for rail transport. It is also essential in designing high speed and safety rail passenger lines, careful analysis of line design methods and the use of simplified relationships. Since rail loads are essentially dynamic, the calculation and control of these forces is of particular importance. One of the areas that should be given special attention in the design of rail lines is the location of the rail seam which is the source of the generation of large dynamic forces. Rail seam welding has been a great success in reducing the dynamic forces in the seam rail but has not been able to reduce these forces to the desired extent and cause white line failure. Since the variations of the vertical force value of the dynamic wheel-rail interaction are similar to the magnitude of the vertical velocity variations, In this study, by measuring the vertical velocity of the track in the weld area of the rail and investigating the extent of its variations as well as the use of computer modeling, it investigates the changes of the seating, force and finally dynamic impact coefficient.