• Fast switching on narrow rails

    PSItraffic train management system at Regionalverkehr Bern-Solothurn

When the newest, highly polished train first rolls into the factory hall amid a great deal of pomp and camera flashes, joy predominates – for the manufacturer, for the happy railway where it will soon be in operation, and ultimately for the future passengers. A win-win situation. But as with the previous train generation, the control system is also ageing. Modernisation requires just as much innovation as a new train. Except the commissioning takes place entirely without media – as with Regionalverkehr Bern-Solothurn RBS. What a shame.

Bern is the capital city – world famous for its continuous arcades in the old town. Every year, Solothurn attracts film and literature enthusiasts. Both cities are connected by the Aare, but via a long detour through Lake Biel that only patient canoeists take upon themselves. A much quicker way takes the trains of the RBS. This is a modern rail and bus company, which beginning in 1974 was the first in Switzerland to introduce an interval timetable on its metre-gauge rail network.

As a result of the enormous commuter demand, over the past years and decades, many sections have been expanded to double track and the rolling stock has been modernised. The original control technology from the 1980s, which can no longer keep pace with the demands of increasingly dense rail traffic, had to be patient. High time for a generational leap. PSI Transcom has taken this step decisively, and with PSItraffic, also done pioneering work. PSI is supported by its project partners, the Institute für Bahntechnik GmbH and ETC Transport Consultants GmbH.

PSItraffic in the RBS control room.
PSItraffic in the RBS control room.

The crux with the intersection

Conflict detection and solution.
Conflict detection and solution.

Let us examine the functionality of the new control system: Assume that a train regularly crosses the opposite train at a particular station. But now a construction train is waiting on the crossing track for a night deployment, preventing a crossing on the otherwise single-tracked section of the RBS. Previously, a dispatcher would have analysed the situation based on the information provided on the push-button control center display. Relying on his experience, he would have decided on which other station the crossing must be shifted to, both to rapidly lead the affected train to its destination while also minimising the delay imposed on the opposite train.

With PSItraffic, the technology takes over this function. Exact train tracking is essential for precise train control. Previously, this was done using automatic block signalling from the section on which the train was located. The remote control of the local signal box transmitted this data to the control centre. "The staff was able to estimate the likely position of the train based on the standard speed in this section," remembers Ulrich Reinert, coordinator Operations and Engineering at RBS. But this is no longer sufficient for today's requirements. Tracking down to the metre or by the second using GPS position information is required for the trains. The location data are – in addition to the data from the signal boxes – constantly reported to the control system. There, a possible timetable deviation is calculated through a comparison with the timetable data. The next steps take place in the central computer of PSI / RBS – of course fully automatically.

The "brain” in the background "

This is also the area of greatest innovation for PSItraffic," explains Holger Troll, Project Manager at PSI. Here, a comparison to the current standard: Conventional control systems can detect and resolve conflicts, but only in the immediate vicinity of an incident. They make no forecast about network-wide secondary delays and how this will affect overall traffic management, unlike the broad capability of the PSItraffic control system. In order for PSItraffic to calculate and resolve conflicts, it must first recognise them. Then it can dispatch again based on the stored rules and in recognition of all theoretically conceivable dispositions. In our example with the construction train, the control system calculates at which of the two alternative stations the crossing should take place in light of the following questions: Which timetable reserves do the two affected trains have? Will other trains be affected in their punctuality? What connections can still be met?

The new control system has to answer questions like these and bring them to the final decision stage. In simple cases without any major impact on operations, the control system will automatically make the disposition and merely inform the dispatcher. In more critical cases, where, for example, connections are broken or trains need to be turned prematurely, PSItraffic provides the dispatcher with suggested solutions, while naturally informing of the consequences. After the solution is selected by the dispatcher, the implementation process begins: The command is sent back to the timetable and workflow forecast. There, the information is prepared primarily for train routing and sent to the signal box remote control, which in turn transmits the actual control commands to the local signal boxes distributed along the route.

Travellers in the trains and at the stations are properly informed about the changes. For this, PSItraffic has an interface for passenger information systems.

There are numerous intermediate stages between the draft timetable and travelling trains

Timetable, resources and construction planning: All of these plans are based on decades of development and the relevant experience of a public transport company. If a plan should be overly ambitious, it will cost time and cause annoyance, but safety is not affected.

Conflict detection / resolution, workflow forecast: The work once performed in the control centre to manually control deviations from the regular timetable is now being performed by intelligence – realised for the RBS by the control system of PSItraffic.

Automatic train routing and train route tracking: Primarily, this is where the planned versus actual comparison of the timetable is performed.

Reliable signal box remote control: What is decided in the control centre – whether manually or automatically – must be transmitted by train control commands to the signal boxes. Here, as with the signal boxes, possible (transmission / signal) errors must be prevented using feedback-based controls. At RBS, this area will be modernised by the company LeitTech.

Signal boxes: They set the switches locally and release trains to move, provided that the following section is not occupied. In the case of RBS, the existing technology will be retained.

Dispatching trains instead of assigning track sections

Accordingly, the work of the dispatchers will also change. In the future, as a rule, they will no longer be assigning sections. Rather, they will dispatch trains using a visual representation of the timetable. This shows the location of all trains in the network in real-time, including the predicted route. In this way, the dependencies between trains will become more easily and quickly recognisable. The dispatcher can assign new time intervals via mouse click and relocate crossings –subsequent control of the routes is assumed by the control system (or by remote control) in the background.

The major benefit: The dispatcher sees the impact of his dispatches on the timetable and can also recognise the dependencies between individual journeys. In this way, the greatest extent of operations can be controlled with minimal effort.

Drive more slowly, save energy

But PSItraffic can do even more: Thanks to the network-wide forecast, the control system also knows how fast which train should ideally travel. The aim is to avoid signal stops by converting the travel time reserve into a speed reduction. This is reflected not only in lower energy consumption, but also improves ride comfort. For this reason, the optimal speed is reported in the driver’s cabin. At a later stage, this information could even be used to partially automate transport operations.

Author: Johannes von Arx, Journalist

Switzerland / www.rbs.ch


PSI Transcom GmbH
Holger Troll
Project Manager RBS