Ways we could make trains safer and smarter
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Re: Ways we could make trains safer and smarter
#2The 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 The reason why crumple zones don't exist on American railways is due to incompetent and centuries-out-of-date Federal Railroad Administration regulation.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.
Re: Ways we could make trains safer and smarter
#3"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.
Re: Ways we could make trains safer and smarter
#4In short, that is what ETCS level 3 will do in all of Europe. Level 2 is currently being adopted in big lines.
Re: Ways we could make trains safer and smarter
#5"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 t…
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.
Re: Ways we could make trains safer and smarter
#6>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".
Re: Ways we could make trains safer and smarter
#7"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 t…
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 bl…
Few railroads run trains that tightly spaced. The London Underground and the NYC subways do have that problem, and they've both been cautious about installing newer train control systems. The London Underground's Victoria Line has a modern system, and it's been troublesome.[1]
The enthusiasm for GPS-based systems comes from low-traffic railroads with a lot of track per train. Their maintenance cost for trackside equipment is high for the amount of traffic.
[1] https://www.theregister.co.uk/2016/08/09/london_underground_...
Re: Ways we could make trains safer and smarter
#8"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 t…
The GPS, radio communication, etc., that the article talks about are not the important bits of positive train control IMO. The important bits are "positively" enforcing safety -- reaching a safe state even if a rail vehicle violates the instructions the signalling system provides it. America's PTC mandate was triggered by the tragic Chatsworth crash back in 2005 or so, which would have been prevented if the red signal shown to the distracted train operator had been positively enforced.
1920s technology can provide enforcement. New York City subway and the Berlin S-Bahn both use old-school wayside trip cocks that raise next to red signals, and if a train passes a red, a mechanism on the side of the train strikes the raised trip cock, triggering a mandatory emergency brake application.
Re: Ways we could make trains safer and smarter
#9"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 t…
The existing track circuits do not provide the same flexibility and traffic density that PTC can allow. In the 1920's there was a Fireman and Engineer on the front end, and a Conductor and Brakeman on the caboose to check the signals and timetables. These days there is just one engineer. CTC won't dump the brakes when a train overruns it's ownership of speed, track, or time. PTC will.
Re: Ways we could make trains safer and smarter
#10Earlier quoted context omitted.
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 bl…
Few railroads run trains that tightly spaced. The London Underground and the NYC subways do have that problem, and they've both been cautious about installing newer train control systems. The London Underground's Victoria Line has a modern system, and it's been troublesome.[1] The enthusiasm for GPS-based systems comes from low-traffic railroads with a lot of track per train. Their maintenance cost for trackside equi…
But, as that article says, the lines with automatic control didn't have any trains passing red signals (except in a depot, presumably under manual control). The manual lines had hundreds.
London has at least some ATC on about half the lines, I don't think that's cautious.