If you see the wheel of any engine/bogie, (tech name I do not konw), it sits on the track but inside there is a big grip like finishing, which holds the wheel on the track. The exterior sided is plain. There is no steering wheel like motor vehicles - cars, buses etc. The track alignment guides the engine and the compartments. Whenever the points are set for the train to move from one track to the other, as you can see in the photo in the entry, they are open ended. The train just moves over comfortably. Depending upon the angle of the points and curvature, speed restrictions will be placed. That is why, trains slow down when moving from main to loop or vice versa.
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