Comment by FeteCommuniste

The word "computers" is doing a lot of work in that sentence.

I would think that the software is the weakest link in the chain.

https://en.wikipedia.org/wiki/Automatic_train_operation

What this chart doesn't show you is how much more expensive it is to advance the grade of automation. Systems like the Docklands Railway are only safe because all their tracks are grade separated with exclusive track. They still need a person on board to be sure that nobody is stuck in the doors or wedged between the train and platform before the train starts moving.

"Have computers control everything" is four words to say, but it's millions or billions more in money, and adds years to the projects. London's Crossrail, for example, was years late due to the complexity of switching between 4 separate signalling systems (ETCS on the Heathrow branch, AWS on the GWML, TPWS on the GEML, and CBTC in their tunnel and exclusive track.)

We're still using TPWS on the ECML, for example, because:

https://en.wikipedia.org/wiki/Train_Protection_&_Warning_Sys...

> TPWS was developed by British Rail and its successor Railtrack, following a determination in 1994 that British Rail's Automatic Train Protection system was not economical – ATP would cost £600 million (equivalent to £1.2 billion in 2024) to implement, compared to value in lives saved: £3 – £4 million (£6 – 8 million in 2024), per life saved, which was estimated to be 2.9 per year.

TPWS is where a little light comes on saying it would be a good idea to brake now because you passed a signal at danger. Only very fancy versions of TPWS will actually apply the brakes for you.

And then we had the Southall and Ladbroke Grove crashes a few years later: https://en.wikipedia.org/wiki/Ladbroke_Grove_rail_crash

> Both crashes would have been prevented by an operational automatic train protection (ATP) system, wider fitting of which had been rejected on cost grounds. The crash severely damaged public confidence in the management and regulation of safety of Britain's privatised railway system.

But even then, an inquiry asked to look specifically into ATP determined we were right to reject it, it was just Too. Fucking. Expensive.

> Since both the Paddington and Southall crashes had reopened public debate on ATP, a separate joint inquiry considering the issue in the light of both crashes was also held in 2000; it confirmed the rejection of ATP and the mandatory adoption of a cheaper and less effective system, but noted a mismatch between public opinion and cost-benefit analysis.