SIEMENS

The shining silver, 11-m-long prototype rolls almost silently along the test track near Strasbourg, France. Airval, the new airport people mover from Siemens, reaches a top speed of 80 km/h. "And yet you don’t hear the train coming," says Marc Zuber, Marketing Director for STS Turnkey Systems at Siemens Industry Mobility in Paris. Even on curves, nothing squeaks or rattles. When this elegant train is in motion, the ride is so smooth that passengers feel as though they are already in the air, especially as the landscape races past the floor-length windows. Even more exciting is the view of the test track through the panoramic windows at the front of the train — a view the passengers can enjoy because Airval is a fully automated train. There is no driver.
According to Zuber, large airports with widely separated terminals will benefit most from this automatic train system. A preview of the system can be seen at Charles de Gaulle Airport in Paris, where the predecessor of Airval has been in service since April 2007. Called CDGVAL and based on Val 208, the train connects the three terminals in only eight minutes. "The trip used to take more than 20 minutes by bus," recalls Zuber.
In a survey, passengers praised not only the time savings but also the reliability of the Siemens-manufactured train and the short headways. CDGVAL runs every four minutes around the clock. In the first year alone, the switch from buses to the electric people mover reduced CO₂ emissions by some 2,000 tons.
Airval, an advanced version of VAL 208, is expected to offer even more benefits to large airports beginning in late 2010. "It is often difficult to predict airport passenger volume," says Zuber. Airval has thus been designed to be particularly flexible. Transport capacity can be easily increased from 1,000 to 30,000 passengers per hour and per direction. Additional cars can be sent on demand from a depot to a route that is experiencing particularly high loads; here, cars are automatically coupled to the train within just a few seconds. An Airval train can consist of one to six cars. The trains can also reverse direction at any time. According to Zuber, this facilitates the around-the-clock operation that is necessary at airports: "Maintenance can be performed at night on one track of a two-track route without shutting down operation," he adds.
Thanks to the latest version of Siemens’ Trainguard MT CBTC train control system, Airval can be operated with headways of just one minute. "When a train leaves the station, the next train is practically pulling in behind it," says Zuber. To make such short intervals possible from a safety standpoint, the train is in permanent contact with control points along its route via a broadband radio link. This system ensures complete safety through the exact tracking of the relative position of the trains along the line.
The cars are also monitored using high-resolution video cameras, whose images are transmitted via radio to a monitoring center. In addition, the radio link will benefit passengers by allowing them to enjoy Internet access over the train’s W-LAN.
In addition to flexibility, passenger comfort was another key consideration during development of the airport people mover, which will also be introduced under the name "Cityval" as a metro system for large cities in late 2010. "If you want people to get out of their cars, you have to offer them an attractive alternative," says project manager Philippe Carpentier. "No one feels comfortable in hot, noisy, overcrowded subways. Our trains are air-conditioned, we provide large monitors connected to a dynamic information system, and our designs are attractive." The large windows are intended to help passengers feel in touch with the city during the route segments that are above ground.

Rubber Tires. Perhaps the train system’s greatest trump is the clever use of a surprisingly simple technology. A look at the test track outside Strasbourg shows why the train is so quiet. Airval is equipped with rubber tires that roll along a concrete guideway with two wide, smooth lanes. In the center of the guideway is a guide rail to which Airval is connected via two rollers arranged in the shape of a "V." Just beside the guide rail is a power rail. The rollers automatically follow the rail and steer the axle in the proper direction like a drawbar coupling system "The rubber tires enable the trains to accelerate faster, climb steeper grades, and negotiate tighter curves than a vehicle with steel wheels," says Carpentier. Each of the tires is driven and braked by an electric motor. Mechanical brakes are used only for parking or in case of emergency.
The train system is also very energy-efficient. When it brakes, its electric motors switch into generator mode to convert the train’s kinetic energy into electrical energy. The vehicle feeds the energy back into the grid, where it can be transferred to an accelerating train. "This process can be very easily optimized in a driverless system because the control system can coordinate braking and acceleration," says Carpentier. With conventional service, you never know when the driver will brake.
Siemens uses this control system in Turin, Italy, where driverless Val 208 metro trains — the forerunner of the Airval — have been in use since the 2006 Olympic Games. There, use of braking energy enables 30 % of power consumption to be returned to the grid. Airval and Cityval are expected to be even more frugal thanks to ultracapacitors (see Pictures of the Future, Fall 2007, Piggybanks for Power). These double-layer capacitors have a very high power density and can be charged and discharged within seconds. This allows the train to store its braking energy and use it for its own acceleration. "We are confident that this will enable us to reduce energy consumption by an additional 10 %," adds Zuber.

Trucks in the Family. Throughout the development process, Zuber and his colleagues took care to ensure that the Airval concept would also be competitive in terms of procurement costs. They thus made unconventional choices in many areas. For instance, they commissioned Strasbourg-based French company Lohr Industrie to build the cars to Siemens specifications. "Lohr’s background is in trucks, which enabled us to take several new approaches," says Zuber. The tires of the Airval are standard heavy truck tires, for example.
The chassis and the passenger cabin are manufactured separately for now. "This allows us to react more flexibly to the needs of our customers," says Zuber. For example, an airport operator can choose how many seats there should be or whether the configuration should allow passengers to move between cars. And the train’s one-of-a-kind steering system was adapted from a rubber-tired tramway manufactured by Lohr Industrie. The concrete guideway for the Airval train system is also much less complex than that of a conventional metro. In fact, according to Airval engineers, in a few years it may be possible to do away with the power rail. Future energy storage systems may be able to squirrel away enough energy to move the Airval from one station to the next, where it would recharge them, as if it were pulling into a gas station.
The Airval prototype is currently demonstrating its endurance on a test track in Strasburg, where it is scheduled to cover a total of 30,000 km by mid-2010. Tests are principally focused on the interface between the vehicle and its automatic control system — and, of course, on the comfort of future passengers, for whom each trip should feel as smooth as air.