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Light Rail for better public transport

Stuttgart welcomes new Stadtbahn LRVs

C.J. Wansbeek sees the fruits of a collaboration between rival tram builders Siemens and ADtranz.

The DT8.10 Stadtbahn twin-set for Stuttgart
Gauge (mm)1435
Traction current (V dc)750
TypeBo-Bo+Bo-Bo
Overall length (m)38.69
Body length (m)38.15
Body width (m)2.65
Body height (m)3.4
Height over pantograph (m)3,715
Truck centre separation (m)12 + 6.6
Minimum curve radius (m)50
Floor height over rail (m)1.0
Bogie wheelbase (m)2.0
Wheel diameter (mm)740
Door width (m)1.3
Door height (m)1.95
Uniaden weight (kg)56 500
Motors (kW)8 x 120
Acceleration/braking (m/s2)1.3
Magnetic track brakes (kN)8 x 66
Emergency braking (m/s2)3.0
Seats108
Standing (4/m2)138

Heavyweights of the German rail manufacturing industry descended in mid-April on Stuttgart, the attractive south-German city that is the capital of Baden-Württemberg Land (province), or Swabia. In this prosperous city, population 555 000, metre-gauge tramways are being replaced by the standard-gauge Stadtbahn. The city itself is as attractive as its light rail system; a loose collection of green valleys, soft rolling hills spacious parks and built-up areas. Just 500 m from the main railway station (Hbf) there are vineyards. Hardly a city, rather a pleasant way of life.

Stuttgart, of course, is more than just an attractive venue. Above all, it is a Valhalla of motor car building, and the Mercedes-Benz star (mounted on a high tower) shines over the city, Mercedes, Porsche and other leading companies (including Zeiss optical equipment) are headquartered here. Mercedes is a trade mark of Daimler Chrysler, the multi-national giant that is the mother of ADtranz, so perhaps the city was the appropriate place to launch the latest in rail technology.

These days, very few of the major rolling stock contracts are awarded to just one firm. Rival companies are adept at putting together consortia which have the necessary skills to impress the customer. ADtranz and Siemens may appear to engage in relentless competition, but whether it is turnkey projects in far-away countries, or producing the best for the home market, their engineers have to work together, even though there may be 'Chinese walls' to prevent disclosure of internal secrets. Co-operative competition can produce miracles, such as a 30% drop in prices over the last few years.

So Stuttgart is a proper place to launch new rail vehicles. On 15 April, Siemens organised a national press show at Stuttgart Hbf to unveil the first German high-speed tilting train ICE-3, a six-car unit designed to up speeds on curving conventional rail routes, such as Stuttgart-Zürich. On 16 April, the first LRV of the DT 8.10 class was handed over to SSB, the transport undertaking of Stuttgart. At a festive ceremony, LRV 3305/06 was unveiled, third of a series of 23, representing a market value of DEM 110 million (50% financed by the Land government). Like all Stuttgart Stadtbahn LRVS, the new vehicle is the fruit of a collaboration between the two rivals, Siemens and ADtranz.

Siemens, together with its daughters SGP (bogies) and Duewag, developed and built the car body and all mechanical parts, representing a 56% share. The electrical equipment came from ADtranz, with a 44% share in the DT8.10 order. The design was done by Professor Herbert Lindinger of Hannover, also known for his design of metro cars for Hamburg and Frankfurt, Stadtbahn LRVs for Hannover, and Frankfurt's R class low-floor trams.

Herr Rolf Eckrodt, President and CEO of ADtranz, took part in the Stuttgart ceremony. He was there a full day, to underline the importance of the event. Siemens also dispatched a heavyweight, Dr. Michael Blumenthal, President of its urban transport division. Together these companies are responsible for the fleet of 114 Stadtbahn LRVs for Stuttgart, delivered between 1984 and 1997. These are among the best examples in urban rapid transit anywhere.

ADtranz was established 1996 as the result of a 50-50 merger of the transportation activities of Daimler-Benz and ABB. In January 1999 Daimler Chrysler, at a cost of DEM 705 million, acquired the ABB share. Today, ADtranz with 24 000 employees is the world's largest provider of rail systems, with production in 60 countries and branch offices in another 40. The 1998 turnover was DEM 6400 million, but ADtranz is making losses, and lay-offs have been announced. Recently, Herr Eckrodt recruited a new top management for the Berlin-headquartered ADtranz, which now has four divisions: Urban Traffic, Regional Traffic, Systems & Components, and Marketing & Service.

For Siemens too, these are difficult years. In the 1997/98 fiscal year, the rail division of Siemens, with 12 000 employees, lost DEM 759 million. It too has announced a down-sizing. Significant redundancy of employees is expected to meet the over capacity in the industry.

Symbolism looms large. Car and truck building has never been so profitable as these years. However, both Siemens and ADtranz encounter red figures in the rail sector. Perhaps the launching of the DT8.10 class was meant to convey the message that private motor car and public transport should reinforce each other. As Herr Eckrodt remarked, the rail car industry can benefit from automotive technology, introducing more standardisation, more modular construction methods, and by relying more on existing know-how. He said that rail transport can survive if costs are cut,

Nine Stadtbahn routes now operate in Stuttgart. Before 2001, another 15 km of new line will be inaugurated, of which 11 km will be outside the city boundaries (the SSB serves a population of 869 800, making 191 public transport trips/year on average). There are still two metre-gauge tram routes within the 111.6-km system, but these should be rebuilt to Stadtbahn operation before 2005, according to SSB managing director Manfred Bonz. So far, in each case the rebuilding and upgrading of a tramway to a standard-gauge light rail line has resulted in an increase of commercial speeds from 20 km/h to 27 km/h. Each route upgraded from tramway to Stadtbahn attracted 25% more riders.

Higher commercial speeds means fewer vehicles are needed, which brings savings. SSB boasts a cost recovery rate of 80%, but wants to improve its performance still further. It engages in stiff price negotiations before any order for new rolling stock is placed, and. scrutinises life-cycle costs for all new products. ADtranz/Siemens obtained the DT8.10 order only after convincing the customer the new product would be the cheapest in running costs over 30 years (and provided a written guarantee of this).

According to Gerhard Steib, an ADtranz project engineer, the DT8.10 Stadtbahn car is designed for a working life of at least two million km. In early 1996, the city of Stuttgart, under an EU-wide procedure, invited tenders for a new class of vehicle. It was the very first city in the Common Market to select Stadtbahn cars under new European rather than old national laws. The 200-page product specification made it clear that it would not only decide on the basis of purchasing costs, but also guaranteed life-cycle costs, based on 100 000 km/year to be covered by the vehicle. Of course, in earlier years, ADtranz/Siemens had built up much goodwill at Stuttgart, keeping in touch with the engineers of SSB. As Herr Eckrodt said, there exists between SSB and the industry a Schicksalsgemeinschaft, a common destiny.

SSB, ADtranz and Siemens check the durability and reliability of each individual spare part used in all vehicles. This gives them insight in the life expectancy of future LRVs, and this helps reduce costs. By now, Siemens and ADtranz feel their latest car is such good value, that, before long, Stuttgart will almost certainly raise its order from 23 to 50 twin-sets.

Stuttgart's network was not born overnight - planning started in 1972. Stuttgart sought excellent riding comfort, good aesthetics, motorisation of all axles of the future vehicles, and also very reliable bogies to cope with the many steep gradients and sharp curves of the lines. In 1982, prototype vehicles were tested near Karlsruhe, as Stuttgart had no standard gauge lines at the time. These twin cars from MAN (a company later merged into ADtranz) later became class DT8 mark 1, 2 and 3. In 1983, Stuttgart made up its mind on the vehicle type it preferred, and the first batch of 40 mark 4 LRVs was ordered from Duewag (now part of Siemens). They feature folding steps for operation at street stops without folding platforms, unlike later cars and the DT8.10. In September 1985, U3, the first line opened, between Vaihingen and Plieningen. Today, the nine lines comprise a total track length of 93.7 km, partially laid in tunnel (there are 22 subway stops). All over Stuttgart, there are grade crossings between tracks and street traffic, the remainders of the tram ancestry of the system.

Over the Weinsteige segment, where there are gradients of 7%, the clean, spacious standard-gauge LRVs run as smooth and fast as they do on other lines. At Stuttgart, at every third of fourth stop, there are interchange facilities with other routes, tram lines, regional S-Bahn lines and national DB rail lines. There is through ticketing organised by the Verkehrsverbund. The unity of all these rail lines makes Stuttgart a mecca of integrated urban and regional rail.

During his speech, aimed at German politicians, Herr Eckrodt of ADtranz accused the UK of allowing its rail infrastructure to fall away. According to him, the UK rail network is "drying up." A climate of uncertainty prevails, in which rail quality is lowered. In the UK, many assets that should be used to increase rail transport's attractiveness are simply thrown overboard, he said, as he pleaded for more Government financial support for Germany's urban and regional rail networks. Other speakers at the Stuttgart venue remarked that Germany as a whole now has Europe's best urban public transport, with no fewer than 100 cities with trams, U-Bahn and S-Bahn.

The industrial designer, Prof Herbert Lindinger, made an interesting comment. He said Stuttgart's older cars are already comfortable and well-designed. Why change a product everyone is satisfied with? He replied that passengers simply demand more comfort and safety. He said the motor car industry, through its aggressive advertising, is provoking everyone to demand more comfort, often to an extent which public transport is unable to offer. Yet the Stuttgart DT8.10 brings a comfort level to satisfy even the most pampered of car drivers. It has air suspension for a smooth ride, the seats are cloth covered and there is air conditioning.

Professor Lindinger also said that the design of the new LRV was round and soft (glatt). In comparison with the 'open muzzle' of the earlier cars, the front of the new LRV offers an almost closed face, with the Scharfenberg coupling mostly removed from sight. This offers a more pleasant look, as well as greater safety in case of collisions. As a further contribution to the passenger's comfort, the windows of the LRV are darker than those used in earlier LRV classes, to offer better protection. Special green glass reflects 90% of all harmful sun's rays.

Everything is spacious and transparent. The articulation is almost invisible from the inside, giving the impression the set is actually one long car. The fact that one can now walk between the two cars brings a better spread of passengers over the interior. The driver's cab is separated from the interior by a glass wall, which enables the driver to keep the entire vehicle under surveillance.

When Duewag and ADtranz started joint production of cars for Stuttgart, they wanted to set a new standard of quality. The two companies decided that their vehicle should be based on the length of the average inhabitant of Sweden. Designer Herr Lindinger, calls this 'anthropometrics'. Whatever the word, the 'Swedish norm' has proved correct, and now that Germans grow taller by the year, Stuttgart does not have to redesign vehicles, as the 'Swedish' norm is still spacious enough. Door height is increased from 1.88 to 1.95 m on this model, and there is a 'buggy' bay by every door. Above all, the new car's design is meant to be 'inviting' to passengers. It was disclosed by SSB that in Stuttgart, 50% of all passengers are car owners. They are regarded by SSB as 'captive riders', passengers who consciously prefer light rail because it performs better than the car. This has much to do with the semipermanent congestion on the roads of Stuttgart.

From April, DT8.10 LRVs have been available for driver training; the complete batch should be in Stuttgart by December. The car can run in multiple of up to three vehicles and is fully controlled by microprocessors. No other LRV contains so much state-of-the-art technology. The motorised parts are all designed to be as compact as possible, offering a low level of 'wear and tear', based on three-phase technology. All moving parts were designed to produce a minimum of noise. The components need very little maintenance, and are built to remain in working order as long as possible. The newly developed electrical converters are compact, and in closed containers. Each electrical converter feeds two motors per bogie. All wheels are powered. The LRV can still run with two axles unpowered. Even braking with only six of the eight axles poses no problem. There are three braking systems (electrodynamic, pneumatic and magnetic) for total safety, and regenerative braking returns 30% of traction current to the overhead.

For the design of the DT8.10, all mechanical and electrical parts used in the earlier series were revised and reworked, making use of the latest technology available. They accelerate fast (1.3 m/s for speeds up to 25 km/h). Each twin set, fed by 750 V overhead, has an installed motor rating of 8 x 120 kW (nearly 10% more powerful than previous batches); the eight fully encapsulated air-cooled asynchronous motors each drive one wheelset. During trial runs at Siemens Wildenrath test track, the DT8.10 reached speeds of 140 km/h. SSB will restrain them to a maximum speed of 80 km/h. Entrance level and floor height is 1000 mm. This makes one think about a 'what if' scenario. What would today's LRVs have looked like if low-floor technology had been mature 20 years ago? In reply to such questions, it was made clear at the Stuttgart ceremony that there is no way back.

The standard-gauge network now has 256 high-platform stations (all equipped with easy access for the elderly and the handicapped). All further extensions will be built to that same standard. SSB sees nothing in low-floor LRVS. On the other hand, SSB would welcome a fully-automated system, following the example of the new fully automated line 14 of the Paris metro, inaugurated in October 1998. An automated metro allows drivers to engage in other tasks built around customer service. However, until a foolproof collision-avoidance radar for street traffic is invented, this is likely to remain a pipedream.

The DT8.10 is marketed as a product ahead of its time. A very long life cycle is predicted, and a new level of quality has been reached. According to Siemens and ADtranz, the DT 8.10 class will be the flagship of Stuttgart's public transport until about 2040, perhaps 2050.


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