Level 2 ETCS is being installed on the Olten - Luzern main line, where Swiss Federal Railways is taking the opportunity to replace obsolete signalling equipment. The project forms a pilot for the ERTMS/ETCS programme

Dr Peter Winter, Head of Development & Technology, Swiss Federal Railways

SWITZERLAND: Swiss Federal Railways has been active from the very outset in the UIC project to develop a uniform automatic train protection and train control system for Europe's railways. Launched in 1995, the European Train Control System has become the nucleus of the European Rail Traffic Management System. ERTMS/ETCS enjoys the wholehearted support of the European Union because it is a key element in the drive to overcome technical barriers that have in the past hindered the development of Europe's railways.

Pilot installations are currently being built in Spain, Germany, France, Italy and between Wien and Budapest (p585). Each will serve as a testbed to confirm that ETCS equipment produced by different manufacturers complies with the principle of interoperability for cross-border working. Without prejudicing the process of standardisation at the European level, SBB is keen to implement ETCS because of the benefits it will bring.

Changed requirements

SBB needs ERTMS/ETCS technology both to meet ever more demanding operational requirements and to replace technically obsolete equipment. On the new lines currently under construction such as Mattstetten - Rothrist, trains will run at scheduled speeds of 200 km/h for the first time in Switzerland.

This means that before the first major section of new line is commissioned in 2005, a tried and tested form of cab signalling will need to be available. Cost-benefit analyses have shown that in the longer term it will in any case be worth replacing conventional lineside signals with cab signalling.

Slightly over 10% of all sections of line located between distant and stop signals on the SBB network are equipped with speed control systems which ensure that trains are brought to a halt ahead of the danger point, even in the event of driver error. As no international standards existed in this area 15 years ago when the system was introduced, SBB had no other option but to choose from the various proprietary products on offer from signalling manufacturers.

SBB's choice was the ZUB system manufactured by Siemens, which subsequently supplied the on-board devices for SBB's rolling stock fleet and for some of the private railways. In the next few years we plan to extend speed controls to other critical line sections and to find a way of converting the ground-to-train interface to the ETCS standard.

The whole of the SBB and standard gauge private railway network is equipped with the Signum automatic warning system which is now over 60 years old. Cab signalling will one day take over the functions performed by this system, but in view of what will probably be a rather lengthy introduction period, we believe it is necessary to replace Signum equipment on some corridors in the more immediate future.

All these applications must conform to the ERTMS/ETCS standards, for this is the only way to achieve interoperability throughout Europe and, at the same time, allow for open competition among different suppliers.

ZUB plus Eurobalise

The introduction of ZUB required considerable input from SBB, from the technical, financial and staff training points of view. As it is very similar to ETCS Level 1 in many of its functions, it makes sense to use Eurobalise technology in future instead of the original ZUB components for data transmission between train and track, both for telegrams specific to SBB with ZUB format and for internationally readable telegrams in ETCS form.

Thus ZUB on-board equipment can still be used on domestic routes where there is no cab signalling and at the same time achieve European compatibility as regards line equipment on the basis of ETCS Level 1.

SBB decided to test this combination of ZUB on-board equipment and Eurobalise technology. The site chosen for the trial forms part of the Zürich - Chur main line between Walenstadt and Landquart; it has about 30 lineside signals, and we decided to equip six vehicles for the trial.

To broaden the scope of the invitation to tender, the interfaces on vehicles and ground equipment were defined in a way that allowed the use of ETCS components. Of the three firms that bid, the contract was awarded to Siemens, whose proposal had the edge in technical terms and on price. The pilot facility was completed on time without any particular problems and has since been placed in service.

For almost two years now the ZUB-Eurobalise test route has been in daily operation, proving that the ZUB speed control system with the new data transmission works just as well as the original concept. However, one issue still outstanding is the testing of the Eurobalise as an additional option for quasi-continuous data transmission. Only recently was it agreed at European level that a concept based on the use of a radiating co-axial cable laid at the foot of the rail would be adopted, with operation in the same frequency range as Eurobalise.

In the meantime, it also became clear that it would not be possible to replace all the Signum track equipment by individually-programmed Eurobalises offering the possibility of speed supervision adapted to local conditions. In order to allow the replacement of these simple systems by interoperable ERTMS/ETCS, this concept must be extended with correspondingly simple warning functionalities in Level 1.

Technically, this is already feasible within the framework of the actual ETCS technical specifications, But because this fundamental issue affects other European railways and not just SBB, we have suggested that the simple AWS functionalities should be included in the functional specifications for ETCS Level 1.

Level 2 pilot proposal

With the ZUB-Eurobalise marriage working well, SBB is now preparing to move to a full-scale trial of cab signalling that meets ETCS standards. The chosen route runs for about 35 km between Olten and Luzern. The project is intended to confirm the applicability of ETCS technology in terms of operations, technical viability and value for money.

To limit the risks, maximum importance is attached to clear and unequivocal operating conditions and functional simplicity. For this reason, all trains using the route will need to be fitted with ETCS equipment. After a short test phase, all lineside signals will be removed.

The invitation to tender for the test installation and its various parts was issued publicly. The contract for wayside ETCS Level 2 equipment and on around 60 vehicles was awarded to Adtranz. Also involved in the project are Alcatel, which is to deliver two solid-state interlockings, and Siemens, which is to supply the GSM-R based radio system. Siemens will also supply Iltis for remote control of the interlockings from Olten.

To collect sufficient operating experience before placing orders for the equipment required for the first new line, the pilot section must be operational by autumn 2000 at the latest. Between now and then full proof will have to be provided of compliance with the requirements set out in the specifications, in particular regarding safety. The requisite test specifications are to be completed before the end of this year, and in January 2000 the suppliers will start tests on system components.

Once these have been concluded, the components will be assembled and trials carried out on the installation as a whole. These will for the most part be undertaken at night, and safety will be guaranteed by keeping the old signalling in service in parallel.

As time is of the essence, only the minimum functions absolutely necessary for the pilot section will be available at the start of the trials. Following an initial consolidation period, additional functions will be provided, which could include the possibility of running through on to ETCS Level 1 sections. However, no decision has been made on the need to develop and procure a special STM interface (Specific Transmission Module) to read the ZUB track devices.

Meanwhile both SBB and Adtranz are keen to test the interoperability of the equipment with vehicles from neighbouring railways as soon as the opportunity arises.


Once the pilot installations are in service, SBB will have a sound basis for scheduling further extension of the ATP/ATC system. This in no way contradicts the longer term trend towards cab signalling that is compatible throughout Europe in accordance with the ETCS standard. It is however more difficult to gauge whether this target should be attained in a single stage or via an interim 'ZUB + Eurobalise' or ETCS Level 1 solution.

From the infrastructure angle, it is increasingly clear that cab signalling forming ETCS Levels 2 or 3 can only be introduced at reasonable cost in conjunction with modern interlockings, yet premature replacement of the many older interlockings in service is hardly a viable economic proposition. To make selected corridors 'Euro-compatible' within a reasonable amount of time, there is little other option than to take the indirect route via ETCS Level 1/ZUB + Eurobalise. It is only in this way that replacing the Signum and ZUB track equipment with the more economically viable Eurobalise solutions can start in the foreseeable future.

For vehicle owners and operators cab signalling equivalent to ETCS will become an absolute prerequisite for running trains at speeds in excess of 160 km/h. In contrast, no additional functions are achieved by introducing the Eurobalise receiver installations alongside the ZUB device. The cost of this interim solution is about one-sixth of the price for cab signalling. But the major part consisting of the balise transmission module and balise antenna can continue to be used in the future for cab signalling.

The optimum migration strategy can therefore only be decided at a higher level from an overall corporate perspective. The extra costs of the vehicle equipment with the installation of Eurobalise receiver devices in addition to ZUB have to be weighed against the savings to be made at infrastructure level by replacing old track equipment with ETCS technology. Once all non-ETCS track equipment is removed, the rolling stock owner can then remove the surplus on-train equipment such as antennae.

However, it remains to be seen whether and when European compatibility will be made mandatory, even on existing lines.