What are these boxes beside the railway? You see, why is the wire coming out of the box connected to the railing?

According to the pictures and questions, we can guess that these boxes are part of railway communication equipment.

The wire coming out of the box is connected to the rail, probably to communicate with the signal equipment on the rail. There are usually signal lights, sensors and other equipment on the railway track, which need to communicate with the control center to ensure the safe operation of the train.

Therefore, these boxes may be a part of railway communication equipment, used to receive and send signals to ensure the safe operation of trains.