The wait for ERTMS – keeping conventional systems safe

Author: Harm van Dijk
Day: Aspect Day One
Session: ERTMS Session

In the Netherlands, railway safety is largely based on the
combination of train detection and ATP by 75Hz Track Circuits.
The ATP system (ATBEG) uses the 75Hz signal of the same track
circuits. This binds the systems. Replacing the track circuits is
only economically feasible when the ATP system (including the
onboard ATP equipment) is replaced.75Hz track circuits are
relatively simple circuits, using robust components, used since the
1960's and before. To date, 16.000 track circuits of this type are
in use, covering over 80 percent of the network.Train detection
with track circuits is becoming less reliable. Developments in
rolling stock (very smooth running) and rail maintenance (optimal
grinding for noise reduction and optimisation of the rail profile to
increase the life span ) lead to more difficult shunting of the
track. Traction systems are becoming complex and interaction
between rolling stock may introduce interference currents that
cause risks for reliable detection and ATP.The policy in the
Netherlands is to introduce axle counters when ERTMS is
installed. With ERTMS, 75Hz ATP is no longer required and thus,
track circuits are no longer necessary. The introduction of axle
counters will then provide reliable train detection, no longer
depending on the shunting of the track.ERTMS is eventually to be
installed on the complete main network. However, the rollout will
take time. It requires a high budget and the capacity of many
signalling engineers to upgrade all lines. It is therefore expected
that the full roll-out will take over 30 years. Development of new
trains and rail maintenance will continue and may lead to a
further decrease in detection performance.ProRail now faces the
challenge of keeping the conventional lines safe during the time
that ERTMS is not yet installed. A double investment in new
systems or additional systems is costly.With an unsolicited
proposal in 2012, Movares advised Prorail to develop a new
version for the track relay of the track circuit. The ambition for
this is to improve reliability and enhance the functionalities by just
replacing the track relay and not changing anything else.ProRail
embraced this idea and after a business case study, development
of the Electronic Track Relay (ETR) started in 2015. A laboratory
prototype has been developed as a proof of concept.The ETR
enables the life span of track circuits to be extended by 30 years,
just by replacing one component in the track circuits. ETR means
(A) Functional improvements by means of digital signal
processing, by (1) reliable detection, even in case of loss of shunt
conditions, (2) improved immunity to near-band interference
currents; and (B) Technical improvements, by (1) Easy
adjustment of the track circuit and (2) Included maintenance
interface for remote monitoring and diagnosticsProRail intends to
develop the ETR together with industrial partners leading to a
design that will be open source. This leads to an open market and
shared knowledge for the railway world.The paper will describe
the challenges faced and the solutions we found while developing
the prototype of the ETR.