Nuremberg, Germany  - Germany's first driverless mass-transit train line officially went into service Saturday in the southern city of Nuremberg, with a computer in charge of the underground trains.

Driverless trains are already in use in other nations, including Singapore's North East Metro Line (NEL) operating since 2003, but Nuremberg's system is unique because it mixes human-driven and computer-controlled trains on the same track.

The Nuremberg operating company, VAG, had been quietly testing the services on the busy 6.5-kilometre track for months in advance of Saturday's official inauguration by Transport Minister Wolfgang Tiefensee of the 600-million-euro (900-million-dollar) system.

Although Germany already has a few driverless light trains at special sites, for example at airports, all of its urban train networks to date have been operated by men and women drivers.

Mixing humans and computer control had previously been seen as too risky, although it is the best way forward for smaller cities like Nuremberg which can only afford modest, gradual improvements to their existing train services.

Driverless systems in Lyons, France and the British capital London operate on completely new, all-automatic tracks where speeding or nervous train drivers do not pose any risk of collisions.

The Nuremberg system was opened two years behind schedule because of technical hiccups in its development.

Tiefensee said, "Now we can export the system. Advanced technology combined with transport is just what we need."

Among the technical refinements is a system that quickly stops a train if a person or an animal falls onto the tracks in a station.

Passengers need not fear being trapped in the automatic doors of the cars, because the doors release again if anything is in the way. (dpa)