Don't they have a vigilence alarm?
In the UK, there's a little bleeper that goes off every minute or so and if the driver doesn't cancel it then the train is brought to a halt, likewise there's the 'Dead Mans Handle' which needs constant pressure on it otherwise it activates the brakes, although if it's foot operated then I think some drivers put their bag on it to pin it down.
Of course, this won't stop drivers using their mobiles, for that you'd need either cameras or hidden inspectors.
Either which way, it does sound like the Metro needs a bit of a shake-up.