A method of validating a correct operation of a HMI, i.e. a human machine interface, located in a driver control arrangement for controlling the operation of the rail vehicle in a rail vehicle, the method comprising the following steps: a) receiving input data comprising information about the velocity of the rail vehicle to be indicated by the HMI and supplying the input data to a first processor of the HMI, and b) processing the input data using the first processor according to a first predetermined procedure for producing indication data which define the way an indication device of the HMI has to indicate the information about the velocity of the rail vehicle, c) modifying the indication data and obtaining - in a validation mode while a corresponding modification function is enabled - modified indication data to allow for validation of the correct operation of the HMI, d) inputting the input data to a second processor and inputting - in the validation mode - the modified indication data to the second processor, e) processing in the validation mode the modified indication data according to a second predetermined procedure for checking if the modified indication data are equivalent to the information about the velocity of the rail vehicle to be indicated by the HMI according to the input data received at the data input and outputting a corresponding check result, f) deciding in the validation mode that the validation was successful if the check result of step e) means that the modified indication data is not equivalent to the information about the velocity of the rail vehicle to be indicated and triggering a predetermined fall-back procedure if the validation was not successful, wherein the first predetermined procedure and the second predetermined procedure are exactly the same predetermined procedures in the validation mode as being performed during normal operation of the HMI, when the indication data are not modified. a) receiving input data comprising information about the velocity of the rail vehicle to be indicated by the HMI and supplying the input data to a first processor of the HMI, and b) processing the input data using the first processor according to a first predetermined procedure for producing indication data which define the way an indication device of the HMI has to indicate the information about the velocity of the rail vehicle, c) modifying the indication data and obtaining - in a validation mode while a corresponding modification function is enabled - modified indication data to allow for validation of the correct operation of the HMI, d) inputting the input data to a second processor and inputting - in the validation mode - the modified indication data to the second processor, e) processing in the validation mode the modified indication data according to a second predetermined procedure for checking if the modified indication data are equivalent to the information about the velocity of the rail vehicle to be indicated by the HMI according to the input data received at the data input and outputting a corresponding check result, f) deciding in the validation mode that the validation was successful if the check result of step e) means that the modified indication data is not equivalent to the information about the velocity of the rail vehicle to be indicated and triggering a predetermined fall-back procedure if the validation was not successful,