I used to think that designing railway signals must be the hardest problem in engineering, because every time I'm delayed on a train (a pretty common occurrence in the UK) the announcement blames it on a "signal failure".
Then I found out that the problem is caused by an epidemic of metal theft on the railways!
It's becoming a big problem in the UK - my parents phone and broadband was down for about a week when their (rural) wires were stripped. The thieves get a truck, tie on the cable and drive, rips the whole thing out the [shallow ditch in the] ground, wrap it up and sell it ... then they come back a week later, when the cable has been replaced, and do it again.
Someone tried to steal the gas pipes from a business premises in my city, left gas leaking in to the building for 24 hours or so, didn't even manage to make off with the pipe. Morons.
I worked for awhile at a local power coop. My boss had to go into court one day because someone was caught trying to steal copper from a substation. The guy was lucky he didn't kill himself.
People do die for it[0] [1]. Not to sound too flippant but the lengths they go to just to steal some wire is genuinely shocking. Do they not appreciate the dangers?
A lot of railway signalling is now done over fibre optics for this reason, with the odd side-effect that a number of rail companies are moonlighting as telcos.
Then I found out that the problem is caused by an epidemic of metal theft on the railways!