A mobile tracking unit capable of detecting defective conditions associated with a set of railway vehicle wheels and with a railtrack upon which a given railway vehicle travels comprises a rotation measurement unit for generating data indicative of rotational rate of the set of wheels; a motion sensor, such as an accelerometer or vibration sensor, for generating data indicative of motion along a vertical axis relative to the railtrack; a data processor coupled to the motion sensor and to the rotation measurement unit for receiving the rotational rate and motion data; a navigation set for generating data corresponding to a respective railway vehicle position thereby allowing for determination of the location at which any respective defective condition occurs; and a transmitter for transmitting predetermined data associated with the railway vehicle to a remote location where the transmitted data can be processed. The data processor is designed for detecting, based on the received rotational rate and motion data, the defective condition associated with the wheel set and for detecting, based on the received motion data, the defective condition associated with the railtrack.