Why are train drivers called drivers and not train operators?
In the UK, trains are “driven” in most instances whether you like the choice of word or not, therefore the person who does the driving ALONE is the driver, because somebody else on the train is responsible for everything else. On one-person trains, where the jobs of two or more people are combined so that the driver does ALL of these things, he is called a Train Operator (as on the London Underground). Where a man is ON the train but not actually driving it other than starting it from a station, he is known as a Train Captain – as on Docklands Light Railway – but even in this case, he(/she) has to be able to drive the train manually under certain circumstances.