Once the DESIRO motorcar family was introduced and the first series of VT 642 vehicles was delivered, there was established the department for a new generation of innovative, flexible and attractive motorcars for passengers. The new family of vehicles appeared as a consequence of the existing requirements of the regional passenger transport. Apart from the comfort offered to the passengers - modern design, safety, reliability and reduced life expectancy costs - the DESIRO concept satisfies also the requirements of immediate delivery, in small series, meeting the specific requirements of the client, and all these in the conditions of constant pressures aiming the reduction of vehicle costs.
New Vehicles for the Existing Directions
in the Regional Passenger Transport
In point of the offer, of the situation and of the distribution,
the public railway passenger transport in the industrialised countries, especially
Germany, is characterised by extreme antagonisms. On one hand, there are extremely well
organised and efficient networks in the urban areas, connected between them by high-speed
transport systems, with high frequency and diminished overall times. On the other hand,
the regional extra-urban transport suffers from lack of attractiveness, lack of
efficiency, low level offers and all these under the conditions that great amounts are
spent on subventions and bottlenecks and it's harder and harder to avoid contamination.
The extra-urban transport began to be neglected, first of all because of the individual
motorization increase and then because of focusing the attention on the prestigious
connections of the IC and ICE type, with their well known consequences. In the 90's this
process repeated also in the new German lands, even if there was a time lag. There are
only few examples of successful regional systems. One of them is without doubt the
regional/urban combined and integrated transport system of Karlsruhe; then, the
utilisation of modern light motorcars on the local lines in Duren.
The reform of the railway system meant a possible turning point in this development.
By separation on regions, by competition and by privatisation the local passenger
transport can be not only reactivated, but also transformed in the third basic component
of a healthy efficient railway transport, together with the long distance transport and
the local public transport. The task of the railway industry is that of supporting this
process by developing and promoting innovative and economic vehicles.
The present situation is generally well known: the regional transport is made on
relatively long distances with old unattractive vehicles. As for the purchase of new
vehicles, both the constructor and the operators meet difficulties. Shorter and shorter
designing periods and deadlines for submitting them, specific demands of the clients for
small series with higher and higher technical complexity - all these, at as reduced prices
as possible, lead to dallies of the deliveries due to deficiencies and giving ups, and in
extreme cases even to withdrawals of entire series. For many of those involved in it, the
consequences of these events are the image loss and even the neglecting of the final
purpose. Under these conditions and under the continuous pressure of the road transport
competition (cars, buses and microbuses) the promotion of the railway transport, as an
ecologically viable solution becomes very difficult.
A way out of this conflict of interests is the development of a platform - concept for a
vehicle based on modulation and standardising of the subassemblies and subsystems.
The Idea and Its Development
Following a similar phenomenon that occurred at the middle of the
90's in the public urban transport, Siemens was one of the firs companies to take this
path, developing the modular concept of trams with COMBINO low floor. Other successful
platform - concepts were the family of the EuroSprinter locomotives and the motorcar
vehicles for urban trains with CitySprinter low floors.
In about the same beginning period efforts were made to develop a vehicle for regional
innovative, non-expensive and attractive transport for the public. These actions became
more concrete in the year 1995 through the release of the EuroSprinter vehicle. Considered
by some people as the legit follower of the light motorcars series constructed by DUEWAG
from the year 1950, this was characterised by a modular flexible construction. Using the 
constructive technique of assembling the aluminium elements with screws, a
method that has also been used afterwards at the Combino and CitySprinter vehicles,
significant weight reductions could be reached. Other remarkable qualities of this
motorcar for the regional service are: most of the floor situated at a height of only 575
mm, modern communication equipment, appropriation for the bicycle transport. The order of
Vogtlandbahn and that of an operator from Denmark followed the initial order for the local
lines in Duren.
The DG AB order for 150 vehicles of the 642 series brought along with it important
modifications of the concept:
•welded aluminium construction, instead of the screw assembly technology;
•common intermediate bogies of the Jakob type, instead of the individual wheels;
•conventional motor bogies, instead of the individual motor axles;
•longitudinal resistance at compression, according to the EBO norms;
•more elaborated conceiving of the vehicle.
Through these modifications, the motorcars of the 642 series became the first
representatives of the DESIRO family, constructed modularly and prepared for future
developments. The next step in this direction was the development of the electric
motorcars of the EMG 312-0 and 312-1 series for the Slovene railways, representing the
extension of the platform through the adaptation of the electric operation at the system
of 3 kV c.c. and also through the development of the three coaches articulated train.
Another contract for the Greek railways led to the development of the five coaches trains
for the 25 kV / 50Hz a.c. system.
The synergetic effects and the experience accumulated in the designing and development of
these three series of vehicles led finally to the organisation and finishing of the
constructive principles of the DESIRO family. The positive experience of the modular
construction was constantly used and the types of vehicles that were missing from the
concept have been developed, resulting in this way an entire family of motorcars for the
regional services with maximum speeds between 140-160 km/h. There were developed
especially Diesel motorcars with great power and hydraulic or electric transmission.
Electric articulated motorcars with up to six coaches were developed for the networks
electrified at 15 kV/16,7 Hz alternative current for DB Regio, series from 424 to 642. In
order to have trains on tracks with very reduced admissible axle load or in order to be
able to take over great denseness of passengers it was necessary to modify the articulated
train concept and to switch to the conventional train with independent coaches and regular
bogies.
The Concept and Its Development
DESIRO was conceived under the principle "one for all"
that is a vehicle that can cover a as wide as possible range of uses:
•the DESIRO family is among the fewest that have both Diesel and electric motorcars;
•the possible configurations of the train cover all the probable passenger flows,
from secondary less used lines to sub-urban service (S-Bahn);
•the variable configuration of the interior and the adaptability of the access
platforms and of the floor heights allow trains to be used under the most different
traffic conditions and services (i.e. the lines that serve the airports);
Other important advantages for the operator, passengers and environment and that have been
taken into consideration when designing are:
•the adaptation of the vehicle's power to the traffic or topographic requirements is
made through the modular concept of taking action;
•the modern design of the interior and exterior allow the operator to make up his own
corporate identity;
•the modular concept of the vehicle leads to a great existing number of identical
spare parts and subassemblies, to a reduction of the supply and maintenance expenses and
also to a substantial reduction of the life expectancy costs;
•in order to meet the client's requirements related to the access facility efforts
were made to adapt the height of the accesses to that of the platforms and the interior
was made using as few as possible steps, ramp or lifted sections.
As a consequence, the vehicle family includes two groups: articulated trains, more and
more appreciated on certain market sections, and the conventional trains, made up of
individual coaches. I this way there can be realised motorcar trains with a length between
25,5 m and almost 105 m with a capacity ranging from 115 to 600 passengers. The
intermediate coaches' length can be adapted according to the traffic requirements. In
order to reach the necessary acceleration values, for the Diesel motorcars provided with
propelling device of the vehicle at each end, the maximum configuration of the train is
limited to three coaches. This configuration proves to be confirmed practically because
most of the lines with great passenger flows are already electrified.
Technical details
The vehicle's box is entirely constructed of aluminium and it is
provided with standardised linking elements to fix all vehicle's components. In order to
make sure the local execution of the construction, a steel variant of the vehicle's box
was provided. As it is a modular component, the vehicle's box is based on standardised
constructive and technological solutions, which, within the limits of the available
options, can be adapted to the operation necessities and to the clients' requirements.
These options differ, mainly by the height of the floor or by the disposition of the doors
and windows. The basic modules of functioning that are closely related to the rest of the
subsystems and components represent the essence of the concept. A modular platform -
concept is characterised by a clear definition and by the strict observance of the
mechanical, electrical, communicational, thermal, acoustic and other nature interference
in the overall conceiving of the vehicle.
With the desire to assure a variable design for the vehicle, the frontal parts are made of
plastic material reinforced with optic fibre, permanently assembled by fixing it against
the basic structure with a thick cape of adhesive. Apart from the known shape of the
motorcars of the 642 and EMG 312 series, the TriCon Design GmbH firm elaborated also other
constructive shapes of the vehicles' ends. Within the limits imposed by certain technical
requirements, an individual design can be conceived according to the client's demand.
The operating equipment is always placed on the vehicles at the ends. All big
subassemblies (Diesel motor and transmission, transformer, converter / inverter) are
placed behind or above the extreme bogies. Depending on the necessities and possibilities,
the auxiliary equipment is also placed on the vehicles at the ends. In this way it is
provided a low floor and easily accessible section in the most frequented part, that is
the middle of the vehicle, while the ends, with higher floor, are considered quiet
sections and are frequented by long distance passengers. This configuration is favourable
also from the point of view of the adherent weight distribution, above the end bogies that
are always between engines.
Unitarily defined subsystems and components are used for this family of vehicles. The
range of the catalogue of components comprises all electric and mechanic systems of the
vehicle. 
Starting from the modular concept of the vehicle itself and
from the use of some functional subsystems with very well defines interfaces - like the
disposal of the passenger compartments, the vehicle's drive, the air conditioning or the
hauling and braking systems - a special emphasis was put on the modular conceiving of the
components themselves. The multitude of options defined by the different configurations of
the vehicle, the operating equipment, the supplying tensions and so on can be reached
rationally by modular systems and at the components' level. Successful examples in this
domain would be:
-the bogie family SF 5000 (conventional and Jakob bogies);
-regulating and diagnosis systems on the basis of the competitive bus system (MVB/WTB)
according to the TCN standard and hard / soft components SIABIS;
-converter with IGBT of the SIBAC and SIBEST systems for the hauling and auxiliary systems
The constant utilisation of the standardised solutions at components' level leads to some
advantages similar to those of the entire vehicle in terms of operation safety and stocks.
Considered as a basic principle of the execution, both for the constructor and the
subcontractors, the standardised solutions at components' level generate in this way the
premises of some short delivery times.
All constructions - both for the vehicle's box and bogies and for the subassemblies and
components - were made with the support of the 3D-CAD techniques. These means allow
graphical representations (virtual prototyping) of the options and allow the client to
chose with anticipation the desired design. The SIMUKIT database is used with this
purpose, as an auxiliary means for describing the interfaces and the components included
in the available solutions stock.
The best combinative solutions and the observance of the individual demands of the clients
led already to the accomplishment and selling of 209 trains from the DESIRO family.
Conclusions
By developing the Desiro vehicle family as a consequence of the development of some already existing products it was possible to create, in an extremely short period of time, a concept for a regional transport vehicle whose diversity and multi-functionality can become an example. Once the first series vehicles appeared the bases of the future projects in Europe and in the whole world were established. Let's hope that the new flexible and innovative concept of the family will keep up with the technological progress in the rolling stock construction industry, and also with the specific desires of the clients and that the new DESIRO vehicles can adapt successfully to the specific conditions of railway operation in our country.
Documentary realised by Eng. Antonio Bianco,
based on Siemens sources
