marcel, 
Some of you might still remember the story of three Polish hackers who helped a train operator get their trains back working, after the manufacturer had bricked them. If not, there is a fascinating article here, which reads like a thriller. And there is also a #37c3 video for those preferring that medium.
1/x
📰 https://badcyber.com/dieselgate-but-for-trains-some-heavyweight-hardware-hacking/
📹 https://media.ccc.de/v/37c3-12142-breaking_drm_in_polish_trains