People are always worried that automated machinery will develop consciousness and decide to wipe out humanity for one reason or another. If the London Underground's automatic trains are anything to go by, they might have a long way to go. Last year hundreds of automated trains had to be cancelled because of issues with the systems running them.
Failures ranged from crashed control computers on the Northern and Jubilee lines (leading to several trains grinding to a halt), on-train computer failures, the Central line's on-board Automatic Train Protection systems (which tell trains when to accelerate and when to brake) failing in service, and the Victoria line's signalling system deciding it didn't want to do its job.
There have also been failures with the antennae that automatic trains use work out their position on the track, causing multiple trains to be taken out of service. Thankfully automated systems have fail-safes in place to ensure we don't end up with any runaway trains. For example, should the Central Line's ATP system fail then the trains will automatically grind to a halt.
While this all sounds rather bad, none of the automated trains on the Jubilee and Northern lines have driven through any signals when they should have stopped. This happened 440 times on the Underground last year, and only 10 of them happened on automated train systems. All 10 happened on the Central line somehow, and were fortunately in low-speed areas.
This all kind of puts a dent in all the claims that automated trains are the best way to avoid delays. But saying that, since the worst delay was 30 minutes the average across the whole automated tube system was only five minutes. That pales in comparison to the kind of problems people have to put up with on National Rail services.
It's not definite proof that automated trains are not the way to go, but it does show that they're far from perfect. It likely means that unstaffed trains aren't going to be happening anytime soon. At least the delays caused by these issues [The Register]