There are many problems when traveling by train in Germany: a lack of staff, defective signal boxes, dilapidated rail networks. Recently, many trains stopped because the snow fell rows of trees on the tracks. According to a recent study in the specialist magazine Space Weather But there is another problem: solar storms could affect train signals and cause them to change from red to green, threatening collisions.
At least that is the result of a computer simulation by British and Canadian scientists led by Cameron Patterson from Lancaster University in Great Britain. The physicist researches how space weather influences train traffic. Even small solar storms, which can be expected every ten to twenty years, could lead to serious disruptions in older track vacancy detection systems.
In such systems, of which, according to the authors, there are still thousands, at least in the United Kingdom, the railway lines are divided into route blocks. On the Glasgow to Edinburgh and Preston to Lancaster routes the authors considered, these blocks are about half a kilometer to two kilometers long. At the beginning of a block there is a relay switch that receives power from a source at the end of the block. If there is no train in the route block, the circuit across the rails is closed, the relay receives power and the train signal lights up green: the route is clear! When a train is on the track, its wheels and axles cause a short circuit: the relay receives no power and causes the signal to jump to red.
In Sweden the sun is said to have turned green in 1982
During a solar storm, the sun throws high-energy charged particles into space. When these collide with the Earth’s magnetic field, they can deform it. As a result, strong northern lights occur, but power grids can also be affected. Geomagnetically induced currents as a result of a solar storm could theoretically also disrupt control circuits in railway networks. But is that enough to switch a signal?
The researchers recreated the track vacancy detection systems on the two British route sections in a computer model and then simulated currents such as those that could arise from solar storms. “Our research shows that space weather poses a serious, albeit relatively rare, risk to the railway signaling system that could cause delays or even have more serious safety implications,” Patterson said in a statement from his university.
Patterson’s researchers report such a case in Sweden in July 1982: According to this, a geomagnetic storm caused a signal to change from green to red and back to green, even though there was no train on the route or other error conditions existed. The study authors also point to previous statistical analyzes that found an increase in the number of unexplained signal malfunctions during periods of high geomagnetic activity. They write about their own study that the computer simulations still need to be checked through experiments.
So in the future, when traveling by train, should you not only be annoyed by delays, but also be frightened by impending dangers from space? At least for Germany, Deutsche Bahn has given the all-clear: “We can rule out that Deutsche Bahn’s safety systems will unintentionally release a track due to solar storms and signals will show the green light,” says a spokesman when asked. The circuits of the DB’s track vacancy detection systems are so short that an induction voltage triggered by a solar storm is not enough to manipulate a signal.
In addition to the pure flow of current, according to the DB spokesman, the safety systems also require “a special frequency or pulses to set a signal to green. This is not produced by voltage induction.” In the event of a fault, the signals always showed red. This safety mechanism stops trains until the track is reported as clear for further travel.