The Deutsche Bahn has a vision: From 2030 on, it wants to arrive and leave all trains at about the same time. In addition, every 30 minutes, long-distance trains run between the 30 largest German cities. Always at the same minute as an S-Bahn. The vision is called Deutschlandtakt. But how can this work? We talked about this with a mathematician who optimizes train timetables.
ZEIT ONLINE: Every 30 minutes in 30 major cities to leave an ICE and connect the cities with each other. A timed timetable would have many advantages, says Deutsche Bahn. Can this work?
Christian Liebchen: An integral timetable is planned. Timetable means: Every line runs every half an hour or hour, which is already usually done this way. The add-on is the "integral": there should be node stations where I can change from anywhere to anywhere with minimal transfer time, because all trains arrive, for example, just before the hour and leave after the hour. In some places, there is such a thing already now, for example, largely in Magdeburg or Offenburg.
ZEIT ONLINE: So what would be the difference?
Christian Liebchen is a professor of traffic management at the Technical University of Wildau. He has a doctorate in mathematical optimization on clock schedules and has 2005 the Berlin subway plan with optimized. He also worked for DB Schenker Rail Deutschland AG and S-Bahn Berlin GmbH. © Matthias Friel
Liebchen: From an integral clock timetable across Germany, there is an additional promise to the passengers: you get timetables, which in many places schedule short transfer times. In order to be able to get his train as a result, the train has to travel much more punctually and with fewer disruptions than it does today. It is important to note how to measure a delay at all: It is usually considered a delay if the train is behind the timetable for a certain period of time, say five minutes. I recently missed a connecting train because of four minutes delay and had to catch the next train an hour later. After the five-minute rule everything was on time, but as a passenger I was an hour late. Punctuality values should in future also include the achievement of connections.
ZEIT ONLINE: And what does the mathematical optimizer say to a clock schedule?
Liebchen: Only if you limit yourself to a clocking, you have any chance to optimize a plan of the size of Germany from the ground up in the mathematical sense, whether integral or not. Otherwise there are just too many variations. We worked for months on the subway timetable that we created for the Berlin transport companies in 2005/06 - the first mathematically optimized timetable worldwide that was implemented, by the way. I'm sure we could not have calculated a demonstrably optimal result without timing.
And in my work, I've learned something else: Not only passengers have to remember the timetable, but also the employees who coordinate train rides in everyday life, especially in case of delays. They can react more flexibly knowing that certain trains come every half hour or that the timetable repeats after a certain period of time because they are always dealing with the same trip constellations. Since they can fall back on experience: What went well, what went wrong? A German tact therefore also means the chance for a better handling of delays.
ZEIT ONLINE: This only works if you can react flexibly. But what if a delay confuses the whole clock?
Liebchen: Tight planning is problematic in every roadmap. However, the example of Switzerland shows that even a highly interlinked integral clock timetable with many nodes does not necessarily lead to low punctuality despite many dependencies and heavy utilization in the node stations. Long-distance traffic in Switzerland regularly performs better than the German one in terms of punctuality.