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Important note: this applies to city trains, which operate in a much more predictable environment than trains that cross large areas of the country.
by o11c 1y ago
Important note: this applies to city trains, which operate in a much more predictable environment than trains that cross large areas of the country.
- Stevvo 1y agoAre you claiming that trains running outside cities are less suitable for one person operation? There is no evidence of that, plenty of trains around the world run both inside and outside cities with a single operator. There is also no evidence of a city being a "more predictable environment". Deaths are roughly equivalent; in the city it's people jumping on tracks intentionally, outside its drivers getting stuck on crossings.
- o11c 1y agoI mean things like: beyond city scale, you can't assume all the technology has been tested together, you can't assume you actually know where other trains are, etc.
- IAmBroom 1y agoI work in rail. In any automated system, you don't assume anything; you either know it absolutely (fail-safe systems), or you revert to pure manual control at line-of-sight of the operator, which is far slower. And yes, all the technology has been tested together. Before a train can enter a new region of authority, it must have permission from that authority, which means they must prove that the train can work with the local tech.
- TylerE 1y agoYou can't assume those things in a subway, either. GPS doesn't work underground.
- LeafItAlone 1y agoThe trains ride on a track. The tracks have sensors. The sensor positions are known. Now you know where all of the trains are. GPS satellites could drop out of the sky and you’d still know where the trains are.
- TylerE 1y agoYes, and those "sensors" have very limited precision. There's only one every several hundred yards.
- kkysen 1y agoThe latest tech for CBTC uses UWB for train positioning, which has a precision of a few inches.
- rexpress 1y agoNew York did some trials with UWB several years ago, which were claimed to have been successful. Since then, there has been very little news of permanent deployment or future developments either in New York or elsewhere. Not sure whether this means that the various signalling suppliers are waiting for a customer to take on the technical risk of being the first to deploy UWB CBTC, or that there were costs or disadvantages that make it unattractive.
- LeafItAlone 1y ago>Yes, and those "sensors" have very limited precision. There's only one every several hundred yards. What? There’s one as far apart as you put them. The precision is what you make it.
- TylerE 1y agoAnd every sensor you add is additional cost, not just upfront, but maintenance for ever.
- 1y ago
- yoz-y 1y agoThere are many other problems. A subway or city train stops every few minutes. This means that if somebody gets hurt, has a stroke, assaults somebody, starts shooting up… there is almost immediately a way to board more staff and handle the situation. On a train with hours and tens or hundreds of kilometers between stops this is much less the case.
- TylerE 1y agoMore predictable maybe, but also way more intensive (only 30-60 seconds between trains, vs rural freight where many lines only see one or two trains per DAY, or even per week.
- frosted-flakes 1y agoAre there are metro systems that run trains 30 seconds apart? I think the fastest is around 90 seconds. Rarely used freight lines (aka branch lines) would never be automated, that wouldn't make sense. And some mainlines (I live near one) see as many as 4 100-car freight trains per hour. Those will never be less than one-man operation either, not least because at-grade crossings are everywhere.
- o11c 1y agoIf there's one thing we should know from the computer world, it is that doing something frequently makes it easier to automate.
- TylerE 1y agoThe problem is that they run close enough together that any failures rapidly cascade until suddenly your whole network is a half hour late as it grinds to a halt...
- IAmBroom 1y agoAny such failures are potentially massively fatal, and grinding to a halt is exactly what we want the trains to do. All that means is that you design the system very robustly. And, of course, trains fail-to-safe. Cut a brake line? Train can't release its brakes. Signal out? Conductor can only move in GoA0 (manual), at reduced speeds, until the next signal is reached (and readable). Etc.