They are lengths of fixed track with passengers at platform height (often adjustable) and which can be customised by clicking on them with the question mark button. When the track of your choice is attached to the invisible track, it updates. Your choice of platform can be added. If the carriages you are using are passenger enabled, they will load and unload passengers - visibly.To get an idea of how they work, look at those by 'ajs' and try them out.
Ray
