5 ms·

Ways we could make trains safer and smarter

41 points by artsandsci 9y ago

mrbabbage 9y ago
The crumple zone point in the article misses the mark. The reason why crumple zones don't exist on American railways is due to incompetent and centuries-out-of-date Federal Railroad Administration regulation. FRA insists on railcars being able to withstand 800,000 lb of pressure without deformation, the so called "buff strength" requirement. This works OK for low speed gondolas and goods vans making up the bulk of the US freight network, but doesn't work at higher speeds or when there are passengers. If you want to see conventional, FRA-approved "buff strength" safety tested against "crash energy management" -- a broader concept including crumple zones -- watch this video [1]. The differences are striking. But to reiterate: don't blame crash safety on lacking technology. Blame it on bad regulation. [1] https://www.youtube.com/watch?v=NUpUJrk4QBE https://www.youtube.com/watch?v=NUpUJrk4QBE
- NamTaf 9y ago
  It's a little more nuanced than that. Old cars are essentially a flat base with a structure stuck on top. This forgoes crumple zones, yes, but it also results in a situation where one car body climbs over the other, as observed, causing the structure to shear in two. Anti-climb bars are a key technology in stopping this and were introduced after a number of large accidents where two passenger cars essentially became a pair of scissors and slid into one another. It also means that the cars stay roughly in line, ensuring that the reinfroced parts of the structure stay bearing on one another and transfer the load into the body rather than into the weak cabin area. If you think about it, the structure is very strong when pressed end-on, but as soon as one climbs it's essentially crushing from above/below and the structure is far weaker that way. Outdated regulation plays a part, particularly around the assumptions of where loads come from. As you mentioned, the buff crushing load assumes a longitudinal action only. Moreover, there has historically been minimal roll-over strength in cabins to protect pasengers. Change is disappointingly slow, however, and with asset lives of 50+ years due to the tough financial challenges facing particularly passenger rail, it takes a long time for new regulation to come into practice.
Animats 9y ago
"A train equipped with positive train control uses GPS, Wi-Fi, and radio signals to find out what to expect on the track ahead, then figure out when it should start slowing down based on things like its own speed and weight." The existing 1920s track circuit technology is simple and reliable. The train's wheels short the rails together, cutting off power to a relay at the end of the block, which sets signals behind the train to red. The classic system also detects broken rails and cars that are not part of trains. If someone leaves a freight car someplace, which happens, it's detected. The classic system doesn't need GPS. The safety components ("vital" in signaling parlance) are very simple. The safety-related components are in trackside boxes along the right of way. There's lots of additional gear associated with dispatching and switching, and that's often centralized and computerized. But the basic train-presence detection and signal-setting is local. There are later systems that still use track circuits, but provide more information to the driver and locomotive. These involve devices which sit between the rails and send signals to the train. Most of these are passive RFID-tag type devices. Some are wired into the signaling system. The classic gear is old, but has a good track record. Never buy trackside equipment from a place with a better climate than yours. - old railroad adage. The better railroad equipment suppliers used to be in upstate New York or Pittsburgh, where ice and snow are a normal part of life. Railroad equipment has to survive powerful snowplows, stuff dragging from trains, flamethrowers used to melt ice from switches, lightning strikes on the rails, machines which replace ties and ballast, and routine minor vandalism. There's a reason that gear is packaged in cast steel boxes.
- matthewmacleod 9y ago
  You're right that track circuits are simple and relatively reliable, but they are also inefficient. Having to retain sufficient safety margins while being unaware of the real location of trains means that there is excess "dead space" in each signalling block that could be used to drive more trains over the existing infrastructure. It's what happens with systems like the DLR in London, which uses an advanced moving block system. There is a tradeoff of course, but it's not at all clear that the simplicity of track circuits outweighs increased utilisation of the track.
  - 9y ago
Faaak 9y ago
In short, that is what ETCS level 3 will do in all of Europe. Level 2 is currently being adopted in big lines.
dTal 9y ago
>But rail is a pretty safe way to get around (more so than driving Understatement of the year. Even in the US the number of deaths per year averages around half a dozen; you're about ten times as likely to be killed by a bolt of lightning. From a people-safety perspective, encouraging people to use trains by making them convenient will have an overwhelmingly better impact than trying to improve train safety. Not that they are mutually exclusive. But if you have a million dollars, I bet you save more lives by putting out a TV ad saying "Thinking of driving? Why not take the train?" than by upgrading a stretch of track. Or by using it to bribe popsci.com into not writing articles about trains subheaded with words like "frustrating", "delays", and "accidents".
- jessriedel 9y ago
  Exactly. One of my favorite blog post titles: "Make buses dangerous" https://www.jefftk.com/p/make-buses-dangerous https://www.jefftk.com/p/make-buses-dangerous

41 points by artsandsci 9y ago

The crumple zone point in the article misses the mark. The reason why crumple zones don't exist on American railways is due to incompetent and centuries-out-of-date Federal Railroad Administration regulation. FRA insists on railcars being able to withstand 800,000 lb of pressure without deformation, the so called "buff strength" requirement. This works OK for low speed gondolas and goods vans making up the bulk of the US freight network, but doesn't work at higher speeds or when there are passengers. If you want to see conventional, FRA-approved "buff strength" safety tested against "crash energy management" -- a broader concept including crumple zones -- watch this video [1]. The differences are striking. But to reiterate: don't blame crash safety on lacking technology. Blame it on bad regulation. [1] https://www.youtube.com/watch?v=NUpUJrk4QBE https://www.youtube.com/watch?v=NUpUJrk4QBE

NamTaf 9y ago
It's a little more nuanced than that. Old cars are essentially a flat base with a structure stuck on top. This forgoes crumple zones, yes, but it also results in a situation where one car body climbs over the other, as observed, causing the structure to shear in two. Anti-climb bars are a key technology in stopping this and were introduced after a number of large accidents where two passenger cars essentially became a pair of scissors and slid into one another. It also means that the cars stay roughly in line, ensuring that the reinfroced parts of the structure stay bearing on one another and transfer the load into the body rather than into the weak cabin area. If you think about it, the structure is very strong when pressed end-on, but as soon as one climbs it's essentially crushing from above/below and the structure is far weaker that way. Outdated regulation plays a part, particularly around the assumptions of where loads come from. As you mentioned, the buff crushing load assumes a longitudinal action only. Moreover, there has historically been minimal roll-over strength in cabins to protect pasengers. Change is disappointingly slow, however, and with asset lives of 50+ years due to the tough financial challenges facing particularly passenger rail, it takes a long time for new regulation to come into practice.

Animats 9y ago

"A train equipped with positive train control uses GPS, Wi-Fi, and radio signals to find out what to expect on the track ahead, then figure out when it should start slowing down based on things like its own speed and weight." The existing 1920s track circuit technology is simple and reliable. The train's wheels short the rails together, cutting off power to a relay at the end of the block, which sets signals behind the train to red. The classic system also detects broken rails and cars that are not part of trains. If someone leaves a freight car someplace, which happens, it's detected. The classic system doesn't need GPS. The safety components ("vital" in signaling parlance) are very simple. The safety-related components are in trackside boxes along the right of way. There's lots of additional gear associated with dispatching and switching, and that's often centralized and computerized. But the basic train-presence detection and signal-setting is local. There are later systems that still use track circuits, but provide more information to the driver and locomotive. These involve devices which sit between the rails and send signals to the train. Most of these are passive RFID-tag type devices. Some are wired into the signaling system. The classic gear is old, but has a good track record. Never buy trackside equipment from a place with a better climate than yours. - old railroad adage. The better railroad equipment suppliers used to be in upstate New York or Pittsburgh, where ice and snow are a normal part of life. Railroad equipment has to survive powerful snowplows, stuff dragging from trains, flamethrowers used to melt ice from switches, lightning strikes on the rails, machines which replace ties and ballast, and routine minor vandalism. There's a reason that gear is packaged in cast steel boxes.

matthewmacleod 9y ago
You're right that track circuits are simple and relatively reliable, but they are also inefficient. Having to retain sufficient safety margins while being unaware of the real location of trains means that there is excess "dead space" in each signalling block that could be used to drive more trains over the existing infrastructure. It's what happens with systems like the DLR in London, which uses an advanced moving block system. There is a tradeoff of course, but it's not at all clear that the simplicity of track circuits outweighs increased utilisation of the track.
- 9y ago

Faaak 9y ago

In short, that is what ETCS level 3 will do in all of Europe. Level 2 is currently being adopted in big lines.

dTal 9y ago

>But rail is a pretty safe way to get around (more so than driving Understatement of the year. Even in the US the number of deaths per year averages around half a dozen; you're about ten times as likely to be killed by a bolt of lightning. From a people-safety perspective, encouraging people to use trains by making them convenient will have an overwhelmingly better impact than trying to improve train safety. Not that they are mutually exclusive. But if you have a million dollars, I bet you save more lives by putting out a TV ad saying "Thinking of driving? Why not take the train?" than by upgrading a stretch of track. Or by using it to bribe popsci.com into not writing articles about trains subheaded with words like "frustrating", "delays", and "accidents".

jessriedel 9y ago
Exactly. One of my favorite blog post titles: "Make buses dangerous" https://www.jefftk.com/p/make-buses-dangerous https://www.jefftk.com/p/make-buses-dangerous