Railway rolling stock section or motor train section. Generally speaking, the on-board mechanic is the "on-board doctor" of the high-speed train EMU, which can also be called the vehicle inspector. He belongs to the railway vehicle section or EMU section of the Railway Bureau, and is the official establishment of the railway. Mainly responsible for the inspection and operation, running state monitoring, emergency treatment on the way and equipment fault maintenance of high-speed train EMU.