Method for determining at least one speed in a rail vehicle

A method for determining a speed of a rail vehicle equipped with at least one first chassis unit, the method comprising:

• providing, with a sensor unit associated with the first chassis unit, at least one chassis speed measurement variable related to the first chassis unit;
• recording inertial measurement variables by an inertial measuring unit;
• forming a reference speed characteristic variable based on the chassis speed measurement variable;
• determining an inertial speed characteristic variable by carrying out an inertial calculation with at least one computing unit, at least based on the inertial measurement variables and, during at least one period according to a first operating mode, based on the reference speed characteristic variable in order to estimate a deviation in the inertial calculation;
• determining the inertial speed characteristic variable, by way of the inertial calculation, at least based on the inertial measurement variables and, during at least one period according to a second operating mode, without taking into account the reference speed characteristic variable;
• with a detection unit, detecting an abnormal process of providing the chassis speed measurement variable based on a reference characteristic variable and the chassis speed measurement variable;
• and
• if an abnormal process of providing the chassis speed measurement variable is present, carrying out the inertial calculation according to the second operating mode.