Swiss Federal Railways is using drones to combat the blight of graffiti.
It costs millions of francs a year to clean train carriages.
The company has been given permission by the Civil Aviation Office to fly at night above the train tracks. The drones are at a height of 30 metres and can spot any trespassing on the railway.
The SBB is not revealing how many times it has used the drones since the programme started in July.
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This winter was significantly warmer than average
