Belgium bridges the ETCS gap: migrating from conventional signalling to ETCS is a daunting prospect for even the most advanced railways, but a little lateral thinking by Siemens and Infrabel has generated an elegant solution, as Siemens' ETCS project manager, Belgium, Nathalie George, explains

International Railway Journal, April, 2008 by Nathalie George

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BELGIUM (along with Switzerland) has a pilot role in implementing the European Train Control System (ETCS). Despite the introduction of ETCS Level 2, Belgium has not opted for a countrywide Level 2 solution. Instead, infrastructure manager Infrabel has chosen a solution which increases the safety level in a short time and allows for migration to a full ETCS system with relatively little effort later on.

In the long term, ETCS Level 1 will be installed on a large part of the network, replacing existing train control systems, mainly TBL and Crocodile, and resignalling unequipped lines. The long-term aim is to have an interoperable, non-proprietary system and to harmonise operating rules.

When analysing its needs, Infrabel recognised that protection for specific danger points had to be increased. Yet migration to full ETCS, particularly Level 2, would fall far short of a delivery deadline in 2010. The introduction of ERTMS (European Rail Traffic Management System)/ETCS Level 2 requires the replacement of all interlockings and denser spacing of GSM-R base stations so the cost and effort would not be justified.

Therefore, Infrabel came up with a solution using ETCS Level I hardware based on "Packet 44". Packet 44 is a data telegram in the standard ETCS telegram which can be used for national applications. This solution allows a quick and very cost-effective migration of the trackside to ETCS in a second step. Since this approach requires only transformation of the TBL data into an appropriate telegram, all the in-depth design work for ETCS Level 1 under Cenelec rules is not needed for the majority of signals. Yet it allows migration to full ETCS Level 1 protection wherever full ETCS protection is required.

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With the hardware in the track being ETCS-based, a later upgrade to a full ETCS Level 1 solution is relatively simple. It also allows the operator to standardise on-train ETCS platforms quickly; the old legacy systems no longer need to be maintained.

Incidentally, the Infrabel approach is quite similar to that chosen by Swiss Federal Railways (ETCS Level 1, limited supervision). Again, for similar reasons (the cost impact of Level 2 and the quick migration time in the total network), an ETCS Level 1-based solution has been selected as the standard for a network-wide roll-out.

ETCS hardware

Siemens has been awarded a contract to equip 4000 signals for TBL1+ (TBL based on ETCS hardware) and for ETCS Level 1. The current train control system TBL is transferred to ETCS hardware, ie Eurobalises and lineside electronic units (LEU). In the first step, the TBL1+ functionality is allocated to the signals. The signals to be equipped are chosen on the basis of a safety study conducted by Infrabel.

In a second step, ETCS functionality is allocated to 1000 signals. These are mainly located along the Antwerp--Basle/Lyon corridor and on the access to the Belgian high-speed line 3. On the whole, this means that 13,000 Siemens $21 Eurobalises and 4000 LEUs will be mounted and programmed. Because standard ETCS hardware is being used, maintenance efforts will be reduced over the next few years. The LEUs and balises can be engineered and programmed very flexibly without any specialised knowledge and can therefore be adapted by maintenance staff, particularly since the Siemens balise can be re-programmed.

A transmission point at a trackside signal comprises an LEU, a fixed balise and at least one transparent balise. The fixed balise sends details on the position of the train to the onboard computer in the train. All signal codes corresponding to the possible signal aspects and the associated telegrams are stored in an LEU. In accordance with the signal aspect, the appropriate telegram is passed on to the variable balises which in turn transmit it to the train.

When a train passes the balise, the trainborne antenna activates the balise by emitting a low-power signal. The balise uses this power to transmit its information to the train-mounted antenna.

The balises will be mounted with the help of a special fastening system. The system eliminates the need to drill into sleepers by making use of the existing rail fastenings. Because track components are not allowed to have a signal colour in Belgium, the balises are grey.

TBL1+ implementation

With the TBL1+ solution, the same signal aspects are transmitted as with TBL. The data transmitted to the vehicle is also interpreted in the same way. The onboard equipment of the vehicles has only to be changed slightly. For reception of the data sent by the balise, a balise transmission module will be added. The TBL signal aspects are transmitted via the Packet 44 data telegram out of the standard ETCS telegram.

Siemens provides a tool for programming the TBL1+ data which has to be transmitted to the balises. This tool enables the generation of output files ready to be programmed into balises and LEUs directly from the existing train control data. The tool is maintained and updated by Siemens and is accessed by Infrabel via a secure internet connection. The balises are programmed jointly by Siemens and Infrabel. The programming is done contactlessly across an air gap by means of a handheld computer and a test and programming unit. Using this unit, it is possible for operators to read out and change the balise programming.