<human>:  Why do the trains go round in circles on the model railway?
<bot>: Well, it’s a model railway, so it’s not a real railway. It’s a toy train. Model railways use a track system that is much smaller than a real railway. The track system is usually a bit larger than the width of a single car. The trains are controlled by a system of wires that run along the track. When the train approaches a switch, the wires are pulled or released, causing the train to move to the left or right. In the case of a model railway, the switches are connected to a controller that controls the speed of the train.