Roslagsbanan is a suburban railway system in Stockholm county, Sweden.
Outside Stockholm, the Roslagsbanan network has been reconstructed to modern
standards for swift commuter train services. The track standard has been
improved and station buildings were converted to increase efficiency and
comfort. While replacing the outdated signalling systems, Automatic Train
Protection (ATP) has also been introduced to offer automatic speed control.
These two aspects of the reconstruction works were entrusted to Ansaldo STS
Sweden AB in a contract with AB Storstockholms Lokaltrafik (SL)in
1998,
at the time covering a contract amount of around MSEK 100. The signalling installation was based on Microlok II from Union Switch &
Signal. Microlok II offers a large amount of freedom for tailor-made solutions.
Additionally, the system is modular offering flexibility in placement of system
units for optimum distribution in a given area.
Microlok II has now been installed at 11 stations and on stretches with
block installations. This means about half of the entire track now is monitored
by Microlok II.
The selected ATP system was the L12000 product from Ansaldo STS Sweden. It
operates according to the same principles used by Banverket, the National
Swedish Rail Administration, i.e. at each signal a special transponder is
installed to provide passing trains with signalling information and current
speed restrictions.
Should the train operator ignore the provided information, the system
automatically slows down the train. At Roslagsbanan, however, an ATP version
that is far more modern than that Banverket has been implemented. It uses a
special operator console and provides additional information to the driver.
Green light
The last stage of Ansaldo STS Sweden's undertaking, Rydbo – Åkers Runö, was
completed in August 2003. Bengt Carlsson, head of department at SL and chiefly
responsible for the contacts with Ansaldo STS Sweden, explains: “This in truth
has been a gigantic generation change at Roslagsbanan. Not the least, this
affected the signalling systems and modern safety perception. In conclusion, we
have been satisfied with the cooperation. Ansaldo STS Sweden has performed
excellently in a project that has required quite a bit of give and take in the
course of events.”
Success factors
From the very start, Ansaldo STS Sweden faced tough capacity requirements
for the delivery. To a large extent, Roslagsbanan is a single-track line – only
13 km of the total line length of 65 km feature double tracks – and during rush
hour, traffic can be very intense. On top, there were requests that the system
must meet the European Cenelec standards at the highest safety level, i.e.
SIL4. To achieve SIL4 certification, extensive risk analysis were performed and
special procedures implemented, e.g. meticulous preparation of all
documentation.
It is of utmost importance that a supplier of system solutions really
possesses sufficient competence and resources to manage his commitment. Ansaldo
STS Sweden’s large supplier base of international resources with technical
skills, products and traffic competence combined with advanced project
management have been decisive in the success of the project.
ATP offers safer travel
Bengt Carlsson also informed that at the outset there was quite a bit of
speculation among users on the matter of ATP: “Many believed it would interfere
with the daily work of train-drivers. However, this has never been the case.
The system is always ready in the background, but it only intervenes when it
really becomes necessary.”
Care for the working environment of the users certainly also includes all SL
customers. “Our customers are all the passengers that ride with SL every day.
It has been a top priority to prevent traffic interruptions, and I am proud to
report that many customers hardly have noticed interlocking switchovers and
commissioning of the ATP system,” concludes Bengt Carlsson.
