Once again, I agree with Steven. 'Conductor' is definitely wrong, although the word looks appealing to speakers of Latin languages. 'Conductor' (Spanish) 'Condutor' (Portuguese), for example, mean driver. In English, however, 'conductor' doesn't refer to the driver of the train. The conductor/guard supervises the running of the service but does NOT drive the train. Who drives the train? The driver, of course. The person who drives a train is a train driver.