The present invention relates to a fault diagnosis apparatus for a brake of a train, an automatic train operation system operated due to degradation of braking performance using the same, and a fault diagnosis method for the brake of the train. In particular, the present invention is directed to determining that a fault has occurred in the brake when the difference between the current acceleration of the train and the required acceleration is greater than or equal to a reference value and safely moving the train to a stopping point through a powering operation or coasting operation such that emergency braking is not applied by an automatic train protection (ATP) system if the fault has occurred in the brake. When a fault occurs in the brake of the train, the train is automatically operated such that emergency braking is not triggered by an ATP system.

Monitoring the brake performance of a brake system of a machine (vehicle 11) by determining a brake delay between input of a request for a brake engagement of the brake system and brake system effectuating the brake engagement. The brake delay determination provides for capturing delay produced by communication of the input from a brake input, actuation of an input to brake system performance, processing of operation of the brake system, and operation of the brake/retardation components of the brake system with respect to the machine's wheels. For autonomous machines, brake delay may be measured periodically and used in monitoring brake system performance.