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Comment by zamfi | Hacker News Reader

The counter-example to this is train tracks. (There are minimum standards for roads, too.)

Self driving trains would probably be easier. Aren't there already some airport shuttle trains and metro transit that's fully automated?

https://en.m.wikipedia.org/wiki/List_of_automated_train_syst...

SkyTrain in Vancouver, BC for example is fully automated. It works well unless there are issues with track or sensors, at which point it has to be driven manually.

The SkyTrain is a great example of how easily transportation technology infrastructure fails during even slightly unexpected circumstances. The trains were inoperable for multiple times this past week, for hours at a time due to snow storms.

Trains aren't exactly new technology, yet here we are with them still not functioning properly during what was actually a pretty routine snow storm. It doesn't leave me very optimistic for self driving cars, which will be significantly more compliced technology.

I agree with your point, although I don't think "slightly unexpected" is fair in this case. For non-locals, Vancouver and the region was hit with pretty heavy snowfall, ice and wind that week.

Sources

Footage of conditions in the city: https://www.youtube.com/watch?v=Ek8dN9AoGbo

Hydro woes and 150km/h winds in the region: https://vancouversun.com/news/local-news/snow-day-highway-al...

Transit status snapshot: https://www.vancourier.com/news/metro-vancouver-snow-results...

School closures, Blizzard warning: https://vancouversun.com/news/local-news/snow-day-highway-al...

Interviews about the ice buildup: https://www.youtube.com/watch?v=FWgx99k585s

Finally, a bit of fun; how Canadians deal with weather: https://bc.ctvnews.ca/video-shows-people-skiing-snowboarding...

Is self-driving the same as fully-automated? I think not.

Self-driving implies intelligence, and fully-automated trains simply follow rote rules, and apply the emergency brakes if something unexpected happens. Not intelligent.

Put another way, self-driving has unbounded complexity, while a fixed number of vehicles on a protected, grade-separated railway is not very complex at all.

Docklands Light Railway works quite well with 45 stations. Humans can take over if needed. Running since 1987 so fairly old tech.

A DLR train has a trained operator, they just aren't (usually) driving. A few places have trains with nobody trained onboard at all. In the event of an emergency remote operators can talk to the passengers e.g. to explain that somebody will come to help or that it has been made safe for them to evacuate (automated trains are invariably electric so it may not be safe to just wander off the train outside a station).

FWIW, self driving trains are a very different problem. With self driving cars, the approach has been to use sensors on the vehicle and make autonomous decisions based on that input. This will never work for trains, because their stopping distances are so long that they cannot use a sensor to detect most oncoming issues.

Self driving trains will require more coordination, with central dispatch to tell them when/where to go. That leaves the intelligence on the train much more basic.

Except you can always install sensors that can look as far as you want

Do you mean on the tracks?

There are hard limitations on sensing onboard the train. Tracks that bend around hills, etc. I have some exposure to wireless communication for trains, and one of the limitations is that you can often not get a line of site even from one end of the train to another.

Not OP, but yes, along the right of way.

Since railroad tracks rarely get up and go walkabout, you can instrument them (conduction, video, lidar/radar) to the limits of your preferences and/or budget. Information can be relayed to both central control and individual trainsets.

So how do drivers stop with long stopping distance?

They have signals to tell them “stop”, they have speed limits posted, they have route knowledge. All detectable by computers, even without changes. Fast trains have in cab signalling in any case.

They have no decision about where to go (signal box sets the points/switch track), they have no decision on when to go (signal goes green)

The only bit which may need human input is the “ok to depart” notification when all the doors are clear at a station.

Now that you mention it, I wonder if tracks would actually be a better solution for most use cases. I could see a situation where highways have tracks and you only have to actually drive at the beginning and end of the journey.

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