Pictures of the Future      Spring 2008

Tailored Solutions – Driverless Subways

Driverless in Nuremberg

Nuremberg ’s subway system will be the first in Germany to use trains without drivers. It will also boast the first line anywhere to share automated trains with conventionally operated ones. The concept is ideal for the custom conversion of existing lines. Siemens is providing the project’s unique technology, systems, and trains.

Summer 2007. It’s one o’clock in the morning at the Sündersbühl subway station in Nuremberg. A red and white test train pulls in. You get on and the train heads out. At first, it looks like any other modern subway train. But then you take a second look and notice that there’s no driver’s cab. All you see is the subway tunnel stretching out ahead of the train’s windshield. "The view from the front car is the only visible difference for a passenger traveling in a driverless train," says Georg Trummer, who heads Siemens’ activities in Germany’s first driverless subway. Trummer’s team manages the test drives, which were originally limited to the three hours available at the start of every night when the Nuremberg subway shuts down.

Exhaustive training is devoted to operations such as automatic starting, braking, and precise stopping, opening the doors, securing the tracks, switching and automatic coupling as well as putting trains into and taking them out of service. Final test operations have been running since the start of 2008—in close harmony with the future timetable, but as yet without passengers. Official commissioning is scheduled for June 2008.

At the end of 2001, the city of Nuremberg and VAG Nürnberg—the local public transport operator—decided to equip the U3, and later the U2, subway lines for driverless operations. Automated subway systems are nothing new. Driverless subway trains have been operating in European cities such as Lille, Toulouse, London, and—since 2006—Turin for more than 20 years. Nevertheless, what Siemens is doing in Nuremberg is unique, since the new U3 line will run initially on part of the route used by the conventionally operated U2 line. No other subway in the world has such mixed operations of trains with and without drivers.

The Nuremberg project is pioneering in another respect as well. In 2009, the U2 line is also expected to be converted to driverless operation over its entire length, thus putting an end to mixed operation. And all of these changeovers are to take place without any interruption of normal subway service. "Nobody’s ever done that before," says Trummer as he opens a door at the end of the platform. Behind the door are key components of the ATC (Automatic Train Control) system developed by Siemens: computers for the routes and the signal boxes. These computers continually exchange data with those in the higher-level control system, as well as with train computers, via fiber optic cables and inductive loops embedded in the tracks. The data includes the destination and speed of each train, track switching information, and the side of the train that will face the platform in the next station.

Digital Drivers. An onboard computer (Automatic Train Operation) in the subway train itself uses this data to control the entire driving process. A second computer (Automatic Train Protection) monitors the actions of the first and makes corrections if necessary. The ATC system registers all train movements via a retransmission channel, which means it always knows where each train is at any given moment and how fast it is moving. The latter capability is made possible by Siemens’ two-car train sets equipped with navigation units and transmission and reception antennas, among other things. Thanks to these, the ATC system can monitor and control subway train movements completely autonomously.

Passengers need not be aware of any of this. What they will be aware of, however, is that the train begins moving smoothly as if guided by a magical hand, brakes slightly, then accelerates once again to its top speed of 80 km/h, and seems to float to a stop at the next station. "The trains travel at an optimal speed in accordance with the timetable and the distance between the stations. That’s one reason they drive so smoothly," explains Trummer. The result is greater comfort, along with a unique view into the subway tunnel. Other benefits of the driverless system include shorter train intervals—100 seconds instead of 200—and the possibility of quickly putting additional trains into service, for example for major events.

"Although investment costs are higher, the new system is more economical. One reason for this is that it takes less time to get trains moving in the opposite direction at terminal stations, which means we need fewer trains and we don’t need to hire additional personnel," says Konrad Schmidt, who heads the project for VAG Nürnberg.

Experience in other cities with automated systems has confirmed this. In Paris, for example, where Metro line 14 has been in driverless operation since 1998, the system has proved itself primarily through improved capacity and safety. As a result, the Paris Metro’s historic Line 1 is also to be automated by 2010. Another driverless subway line is currently under construction in Barcelona, and a third is taking shape in Uijeongbu, Korea—all of them with technology from the Siemens Mobility Division.

The VAG Nürnberg control center is located just a few kilometers from the test line. Staff at the space center-like facility can monitor all automated operations on computer screens in semicircle formation and on large wall monitors, so that they can intervene in the event of an emergency. In such a case, the various computers will provide diagnostic information and video images. Control center staff can then take over control of the system.

The control center also monitors messages from the safety systems, which represent pioneering joint developments from Siemens and Honeywell. "Normally, automated subways are equipped with platform doors that block the dangerous area at the edge of the platform until the train has stopped. This wasn’t possible in Nuremberg due to the mixed automatic/driver operation, and because the platforms of some stations are curved," explains Trummer.

Safety First. Absolute safety is ensured by video monitoring and a new high-frequency transponder system that sends a dense grid of sensing beams out over the tracks from transmitter and receiver rails installed underneath the platform edge. If a person or object falls onto the track or between a train coupling, the system will immediately stop all trains in the area. Solid sills extend from doors when trains are in stations to ensure that no one can get caught in the gap between train and platform.

When it’s time to go, an infrared sensor in the rubber edges of the door halves registers even the slightest pressure—the seam of a coat stuck in between is all it takes to keep the train from leaving the station. The control center monitors train-car interiors via video cameras. Passengers who activate an alarm are automatically put into direct contact with the control center via digital voice radio. Control center staff can immediately dispatch maintenance or rescue services to the train.

"In general," says Trummer, "the trend in Europe is toward fully automated systems—at least for closed systems like subways. Unlike streetcars or buses, subway trains don’t have immediate contact with street traffic, which means it’s much easier to monitor and secure them." The "driverless future" is about to become reality in Nuremberg—and the seats with the best view of the tunnel will likely be the most popular ones.
                                                                                                               Dagmar Braun