4 ms·

There are two checks that the conductor does. One is to ensure that all the doors are "platformed", i.e. won't open into the tunnel. This is done by pointing

There are two checks that the conductor does. One is to ensure that all the doors are "platformed", i.e. won't open into the tunnel. This is done by pointing at a striped bar hanging from the ceiling. They lean out the window and point because it's one of those "hacks" that makes compliance with the procedure more likely. (Kind of like how checklists dramatically increased aviation safety.) The second thing they do is check that the train isn't dragging anything when it's leaving the station. People do get caught in the doors (usually their clothes or bags), and you don't read about them dying because the conductor is paying close attention and stops the train. Can you engineer sensors to do this? Absolutely. Machine vision is getting better every year, but these procedures date from a time when digital cameras and computers didn't even exist. They work well, don't require maintenance, and are simple. An engineered sensor-based solution would be expensive, would break often in the dirty environment of the tunnels, and would be pretty imperfect. So I think a pretty good engineering compromise has been made here. Going to the moon happened because there was an unlimited budget and we only had to do it a few times. Seeing if your train is platformed correctly and that it's not dragging any customers to their death has less funding and has to happen thousands of times a day. Hence, we have a person in the train to do that, instead of a machine learning sensor network.

JAlexoid 7y ago
There are a million approaches to this. Minority of the solutions are CV. Most are already solved engineering problems. Elevators manage to not drag you, but multimillion dollar train cars can't? Your thought process is one of over-engineering. Don't overengineer.
- jrockway 7y ago
  Elevators don't run outdoors at 60 miles an hour in a blizzard. Trains are taken out of service all the time because the door opening/closing machinery has stopped working. A sensor that can detect the sleeve of your shirt caught in the door would have to be more precise than what elevators use, and operate in significantly harsher conditions. (In Japan, platform doors are common. Every installation I've seen has multiple e-stop buttons to press if you get caught in them. Clearly they don't trust the sensors, if there are even sensors. And those doors are static and don't move with the train.)
  - avianlyric 7y ago
    London Underground operates in the same conditions and have figured it out, without the emergency stop buttons, or platform side doors. The Victoria line has been operating semi-automatically with driver only operation, and not getting out of the trains (because the windows don’t open) since 1968. These aren’t insurmountable problems, and they’ve been solved for a very long time. https://en.m.wikipedia.org/wiki/London_Underground_1967_Stock https://en.m.wikipedia.org/wiki/London_Underground_1967_Stoc...
avianlyric 7y ago
> Can you engineer sensors to do this? Absolutely. Machine vision is getting better every year, but these procedures date from a time when digital cameras and computers didn't even exist. They work well, don't require maintenance, and are simple. An engineered sensor-based solution would be expensive, would break often in the dirty environment of the tunnels, and would be pretty imperfect. The London Underground has figured this out, and figured it out decades ago. No tube driver gets out of their cab, or puts their head out of a window (they don’t have one that opens). Stations are equipped with cameras and screens that allow drivers to check doors. The doors are designed to detect obstructions, including items of clothing trapped in them. For Crossrail TfL has invested huge amounts of money into their new trains to further improve the door sensors, due to the extreme length of the trains. The doors have been tested for their ability to not just detect trapped items, but also the difference between bad (someone inside with a scarf trapped) from emergency (someone outside with a scarf trapped). [1] All of this is done to not just improve safety, but also capacity. In London at least, the biggest restriction to capacity is the amount of time trains need to spend at platforms for people to get and off. They’ve already optimised the hell out of transit period between stations. And all of this has been done on the oldest underground network in the world, and trust me it’s age shows. No Victorian ever imagined the tube would be so busy (or they wouldn’t have stuck us with tiny 6” high passenger compartments). [1] https://www.londonreconnections.com/2018/crossrail-cutting-fine/ https://www.londonreconnections.com/2018/crossrail-cutting-f...
deleted 7y ago
[deleted]

JAlexoid 7y ago

There are a million approaches to this. Minority of the solutions are CV. Most are already solved engineering problems. Elevators manage to not drag you, but multimillion dollar train cars can't? Your thought process is one of over-engineering. Don't overengineer.

jrockway 7y ago
Elevators don't run outdoors at 60 miles an hour in a blizzard. Trains are taken out of service all the time because the door opening/closing machinery has stopped working. A sensor that can detect the sleeve of your shirt caught in the door would have to be more precise than what elevators use, and operate in significantly harsher conditions. (In Japan, platform doors are common. Every installation I've seen has multiple e-stop buttons to press if you get caught in them. Clearly they don't trust the sensors, if there are even sensors. And those doors are static and don't move with the train.)
- avianlyric 7y ago
  London Underground operates in the same conditions and have figured it out, without the emergency stop buttons, or platform side doors. The Victoria line has been operating semi-automatically with driver only operation, and not getting out of the trains (because the windows don’t open) since 1968. These aren’t insurmountable problems, and they’ve been solved for a very long time. https://en.m.wikipedia.org/wiki/London_Underground_1967_Stock https://en.m.wikipedia.org/wiki/London_Underground_1967_Stoc...

avianlyric 7y ago

> Can you engineer sensors to do this? Absolutely. Machine vision is getting better every year, but these procedures date from a time when digital cameras and computers didn't even exist. They work well, don't require maintenance, and are simple. An engineered sensor-based solution would be expensive, would break often in the dirty environment of the tunnels, and would be pretty imperfect. The London Underground has figured this out, and figured it out decades ago. No tube driver gets out of their cab, or puts their head out of a window (they don’t have one that opens). Stations are equipped with cameras and screens that allow drivers to check doors. The doors are designed to detect obstructions, including items of clothing trapped in them. For Crossrail TfL has invested huge amounts of money into their new trains to further improve the door sensors, due to the extreme length of the trains. The doors have been tested for their ability to not just detect trapped items, but also the difference between bad (someone inside with a scarf trapped) from emergency (someone outside with a scarf trapped). [1] All of this is done to not just improve safety, but also capacity. In London at least, the biggest restriction to capacity is the amount of time trains need to spend at platforms for people to get and off. They’ve already optimised the hell out of transit period between stations. And all of this has been done on the oldest underground network in the world, and trust me it’s age shows. No Victorian ever imagined the tube would be so busy (or they wouldn’t have stuck us with tiny 6” high passenger compartments). [1] https://www.londonreconnections.com/2018/crossrail-cutting-fine/ https://www.londonreconnections.com/2018/crossrail-cutting-f...

deleted 7y ago

[deleted]