1: Have internal CCTV cameras installed in older rolling stock with the camera’s wirelessly sent to a new HQ where staff are continously checking the cameras for tagging, seat tearing and vandalism.
2:Keep the end of Platform Gates locked. I know this sounds stupid, but most of the gates at the end of the Platforms are unlocked with the trains and track easily accessible by vandals.
Somebody said
Wow, what a boring job that would be. You would need hundreds of staff to monitor every deck of every carriage. Might be good if you like a good perve on females/males/whatever your taste is.
Locking a gate is not going to stop you from walking around it, unless you have platform screen doors.