Wanted: Future Interlocking Technology

How do you tender a technology that you do not even know yet? Together with SBB, RUBI Railtec is using two innovative methods.

Nothing less than the future safety of Swiss rail traffic is at stake. SBB’s existing partnership contracts for interlockings are coming to an end. Interlockings are the brains and nerve centres of the railway infrastructure—nothing works without them. Accordingly, supply delays are a no-go. Therefore, contracts with suppliers must be seamlessly renewed.

RUBI Railtec | Interlocking Switches
Railway Levers

Tokens, Levers, and Circuit

Signal boxes have been around almost as long as there have been railways. The first trains were still secured with tokens. Only the conductor with the corresponding token in his (there were definitely no women in the driver’s cab at that time) hand was allowed to drive on a line. Of course, this system soon reached its limits. When trains do not stop at every station, when two trains travel one behind the other in the same direction or when several tracks are available, the track staff system goes from being a safeguard to a risk.

The first signal boxes were mechanical. Switches and signals were connected to each other and to control levers with wire pulls or rods. Thanks to this connection and the transmission of mechanical power, the system was unambiguous—there could be no discrepancy between lever, point, and signal, because they all hung from the same wire pull.

RUBI Railtec Interlockings
Control panel of an electromechanical signal box in the Berlin U-Bahn Museum

The first small developmental step was the electrification of mechanical signal boxes. Instead of muscle power at the lever, points were now driven by electricity. Mechanics were now no longer one-to-one—it was theoretically possible that the lever in the interlocking was turned or the button pressed, but the impulse was not transmitted (for example because of catchy switch or a short power cut). On the other hand, it was now possible to use electrical circuits as a monitoring instrument. If the so-called coupling circuit is interrupted, the signal automatically falls to the stop position.

Ones and Zeros

The next stage in the development of interlockings was already digitalisation. However, the zeros and ones were not yet in the form of bits, but of relays. These electrical switches usually have only two positions—open or closed.

As with our computers, this simplicity of the basic unit allows for great complexity when combined. Relay interlockings make it possible for the first time to set an entire route at the user interface and leave the individual switching entirely to the machine. In addition, there is no longer any transmission of mechanical forces between the interlocking and the external system. The radius of an interlocking was therefore no longer limited by the maximum length of wire drawing, but by the transmission speed of the cables between relays.

Relay interlockings can still be operated reliably today and are therefore widely used. Nevertheless, technical development is progressing. With the penetration of computer hardware and software, the electronic interlocking made its entrance. It is operated like a computer—in the past with a lightpen, nowadays with keyboard and mouse. Transmission is still done with relays or even cables. Safety, however, is now only ensured by software.

The Next Step?

The electronic interlocking is currently the state of the art. However, because the oldest models date back to the 1970s, European railways have been considering for some time what the interlocking of the future might look like.

RUBI Railtec | Interlockings
Almost retro: operating station of an electronic interlocking

One possible development step is the digitalisation of data transmission. Separate cables would then no longer have to be laid between the signal box and the outdoor facilities. Instead, the digital interlocking would be connected to its points and signals via an existing data network. The inclusion of the cloud is also conceivable. Instead of only being operated from interlocking buildings or control centres, signal boxes could then be operated from anywhere in the world. These developments would create new potential, but also a greater risk of connection interruptions and hacker attacks.

Back to SBB’s expiring contracts. Putting a technology out to tender when it is about to jump to the next plateau is pretty bad timing. While SBB specifies its toilet paper in detail in tenders so that it does not clog up train loos, almost nothing is yet tangible in the tender for the signal box of the future.

Necessity is the Mother of Invention

Nevertheless, SBB must ensure that it can build, renew and overhaul signal boxes at any time. That is why innovation is also needed on the procurement side. Fortunately, the Federal Act on Public Procurement (PPA) contains certain provisions that help in such situations—for example selective procedures and integrated dialogues.

In a selective procedure, public entities such as SBB are allowed to admit only certain providers to tender. In terms of fairness and competition, this procedure is not welcomed. In the case of a broad and thus imprecise tender such as that for the interlocking of the future, however, selection allows the number of different approaches to be limited to a tolerable level. However, this can also be a disadvantage for the buyer because providers with novel and unconventional ideas are disadvantaged if they are not admitted to the procedure.

RUBI Railtec | Interlockings
Would they have been considered in a selective procedure? A statue of Steve Jobs with an iPhone

Because SBB does not yet have a clear picture of the technology, it wants to talk to providers about their ideas and offers. This is where the dialogue integrated into the tender process comes into play. Instead of evaluating the offers on the basis of defined criteria, SBB holds one or more dialogue days with selected companies. These run according to a narrowly defined scheme so that none of the dialogue partners is disadvantaged. Bidders who do not win the contract are also compensated for their time and effort.

The Future is Now?

To start with: the first interlocking of the future will not go into operation until 2028 at the earliest. Until then, a lot of water will still flow through the turbines of SBB power stations. Because of the complexity of both the technology and the procedure, the tendering process is already starting now.

SBB has already made a preliminary selection of potential suppliers and informed them about the tender. The information documents have also been posted on the simap.ch submission platform. The actual starting signal for the application phase will also be given there in autumn.

In winter, SBB will assess applications to participate and decide with which providers it wants to enter into a dialogue. Since their preparation involves a lot of technical thinking, it takes almost a year. Accordingly, the dialogues will be conducted from winter 2023 to summer 2024. Afterwards, the providers submit their offers—if they are still interested in the contract.

From then on, the tendering process will resume as usual. SBB will evaluate the final bids; the bidders will revise and adjust them if necessary. In 2025, it will be decided which bidders will be awarded the contract.

This article was originally published by RUBI Railtec.

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