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Comment by huntertwo | Hacker News Reader

I’m unable to figure it out - is this just a screen that tells you what the status of the next signal is? Or does it control the train?

Also couldn’t they just retrofit a battery somewhere instead of a new steam generator? It also seems like they reinvented the wheel making it rugged. Seems like they’re spending too much money on this project, but it seems to be private money so ¯\_(ツ)_/¯

Edit: presumably the rest of the train also has power? Is the power draw from this system so intense it needs a new generator? Or does it need the resilience maybe?

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The complete system only controls the train insofar as it can apply the brakes (and probably cut the steam). What it can do depends on the lineside equipment. On newer routes it replaces the signals, keeps track of where the train is, where it has to stop and how fast it can go. It communicates with transponders mounted between the rails and depending on the route via GSM-R with a "Radio Block Center". It might communicate with older, uk-specific safety equipment. It contains a black box to monitor the driver and train. The screen is just a part (the so-called "Driver Machine Interface") of the whole system. And it needs to meet a high level of safety.

ETH is a lot more than something a simple battery could provide. 1 ETH 'unit' is 5kW of power at 750-1000V AC. A train will usually require much more than 1 unit.

HEP cars (aka 'generator cars') are a solution, but the UK never really had them, we had converted diesels called 'Ethels', which are functionally identical to the current practice of tagging a diesel locomotive at idle on the tail of the train, but all of those were scrapped.

* Ethel => https://en.wikipedia.org/wiki/British_Rail_Class_25#Train_He...

"Also couldn’t they just retrofit a battery somewhere instead of a new steam generator?"

Kindly hand in your tail coat, stovepipe hat and brass head-up-display monocle on your way out, sir!

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