The impact of space weather on signalling systems is a rare threat to rail safety. Cameron Patterson and Professor Jim Wild from Lancaster University sheds light on the potential threat
The study reveals that solar storms, capable of triggering geomagnetically induced currents (GICs), may lead to malfunctions in rail signalling, potentially causing accidents.
Understanding the mechanism
Solar storms can create powerful magnetic disturbances on Earth, generating GICs that potentially interfere with electricity transmission and distribution grids.
The team focused on AC electrified rail lines, specifically the Preston to Lancaster section of the West Coast Main Line and the Glasgow to Edinburgh line, modelling how GICs induced in the rails could cause rail signalling to malfunction.
The research indicates that space weather can flip signals in either direction, turning a red signal green or vice versa. While “right side” failures (green to red) are considered fail-safe, the more hazardous “wrong side” failures (red to green) could occur at a lower geoelectric field strength. This means even weaker geomagnetic storms could trigger dangerous signalling malfunctions.
Frequency of events
The team estimates that space weather events capable of causing faults in track circuits are expected in the UK every few decades. “Wrong side” failures could occur due to a geomagnetic storm with a frequency of about one or two decades.
Even once-in-a-century, extreme events could cause widespread malfunctions, depending on the number of trains on the line. Historical examples dating back to the nineteenth century reveal instances of space weather interfering with railway signalling.
The massive solar eruption in 1859 triggered a geomagnetic storm that disrupted telegraph lines worldwide. The study also assessed the impact of a solar storm of similar magnitude, predicting widespread problems with signalling on the studied lines.
Safety implications and mitigation measures
The research emphasises the serious, relatively rare, risk space weather poses to rail signalling systems, potentially causing delays or critical safety issues.
Patterson suggests that as our understanding of space weather hazards improves, it may be possible to integrate space weather forecasting into decision-making processes for limiting railway operations during extreme events.
Rail sector risk
Severe space weather is recognised as a significant risk in the UK Government’s National Risk Register for Civil Emergencies. The research underscores the importance of the rail sector being included in planning for mitigating risks associated with space weather.
As industries like aviation and electricity generation consider these risks, the rail sector must also be proactive in ensuring the safety of its operations considering this unique natural hazard.
