Page 154 - 360.revista de Alta Velocidad - Nº 5

Hutchinson, Michael. Marais, Juliette. Masson, Émilie. Mendizabal, Jaizki. Meyer zu Hörste, Michael.

In April 2012, a big recognition step has occurred when the European Commission, the European
Railway Agency and the European Rail Sector Associations signed together an ERTMS Memorandum
of Understanding concerning the strengthening of cooperation for the management of ERTMS. It
mentions in particular that GNSS can play a major role in the rail sector [ERTMS, 2012].

In the same period, new initiatives have been launched such as the NGTC project (Next
Generation Train Control) that aims to study how the new developments for ERTMS/ETCS (for
interoperable networks) and those for CBTC (Communication-Based Train Control) systems (for
urban networks) can be mutualized. Satellite positioning is one of the NGTC focuses.
GNSS provides a means of absolute positioning with achievable accuracies at the order of metres
using basic consumer-level devices to the order of centimetres based on more sophisticated
solutions. It is today used in an extremely wide range of applications from smartphone navigation
to network timing synchronisation in critical infrastructure to safetycritical aircraft operations.
In the railways, GNSS is today widely used for applications where its use is not critical such as
basic tracking and synchronisation of onboard systems. The industry is also starting to recognise
the potential for using GNSS for more advanced applications, from those that are regulated and
include an element of liability to train control and operations. For example, GNSS is currently
used for Selective Door Opening systems which have an associated safety-criticality. Many of
the more advanced applications have demanding requirements which are not straightforward
to meet with GNSS due to the challenges presented by the railway environment in terms of
GNSS signal availability and quality. Features such as tunnels, cuttings, trackside buildings
and vegetation can block signals as well as reflect them, inducing multipath effects in GNSS
receivers. There is a general consensus that GNSS must be integrated with other sensors and
sources of information in order to meet the very demanding safety requirements of train control
applications, which can be more demanding than in civil aviation applications. GNSS is also
vulnerable to interference and spoofing threats and solutions must be identified to mitigate
this.
In recent years there has been significant research and development undertaken into the
Virtual Balise application. This uses an onboard GNSS-based positioning system to detect when
a train passes well-defined ERTMS ‘Balise’ locations stored in a database onboard, enabling the
odometer calibration to be performed. This allows physical Balises to be removed from the
track, making savings in terms of CAPEX and OPEX (maintenance). The current focus for this
application is on local and regional lines, largely since it represents an economically justifiable
way of introducing ERTMS onto such lines which will improve safety and/or capacity. Other
advanced developments include the mandated Positive Train Control concept in the USA, for
which GNSS is an optional source of positioning, and the research into the use of GNSS for
Degraded Mode Working in the UK.

3. The Role of On-Board Localisation in Future Train Control Systems

3.1 The SmartRaCon approach in Shift2Rail

The European research for Railways will be done for the next coming years mainly in the
Shift2Rail Joint Undertaking. The European Union, two railways and six industry members
founded the Joint Undertaking.

The Joint Undertaking Shift2Rail comprises five Innovation Programs (IP) and five Cross Cutting
Activities (CCA) of railway research and development for the near future. More than 40 Technical
Demonstrators will be developed in the field of rolling stock, traffic management and control
systems, infrastructure, IT solutions and rail freight.
Four Partners with a strong expertise in research and development in the area of train control,

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