Germany’s railway operator plans to deploy mini drones to catch vandals who deface its trains with graffiti, with the aerial vehicles shooting thermal images of its train depots at night.

Deutsche Bahn plans to soon start testing the vehicles which have four helicopter-style rotors and can shoot high-resolution pictures.

A “pilot” remotely steers the vehicles at heights of up to 150 metres (500 feet) and speeds of up to 54 kilometres (33 miles) per hour. An operator evaluates the images, which the company plans to use as evidence.

Deutsche Bahn said it suffered property damage last year worth 7.6 million euros ($10 million) from people spray-painting its carriages.

The rail operator said it would only use the drones over its own depots, not in public areas, in line with German anti-surveillance laws.