A strong argument in favour of computerisation, however, is that the worst delay caused to trains in service as a result of these types of failure was 30 minutes long – with the mean average delay time across all 700+ automated system failures being just five minutes.
That is amazing. Bear in mind that the Victoria Line runs over 30 trains per hour in the peak! I don't feel that "troublesome" is an appropriate description.
In the UK at least, a large number of railway routes really are constrained by the safety margins required for trains. In the late 90s, when the West Coast Main Line was upgraded, there was an abortive attempt to implement a modern moving-block signalling system – but it was predictably too difficult for such a complex line.
I don't doubt that you're right about the incentives being different on low-traffic lines though. It does demonstrate that there are various benefits to more automation that need to be traded off against the complexity, cost, and rust of failures.
London has at least some ATC on about half the lines, I don't think that's cautious.
The enthusiasm for GPS-based systems comes from low-traffic railroads with a lot of track per train. Their maintenance cost for trackside equipment is high for the amount of traffic.
[1] https://www.theregister.co.uk/2016/08/09/london_underground_...