
Ways we could make trains safer and smarter - artsandsci
http://www.popsci.com/make-trains-safer-and-smarter
======
Animats
_" 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
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.

~~~
Animats
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_...](https://www.theregister.co.uk/2016/08/09/london_underground_trains_stopped_750_times_automatic_train_operation_failure/)

~~~
matthewmacleod
From the article you cited:

 _A strong argument in favour of computerisation, however, is that the worst
delay caused to trains in service as a result of these types of failure was 30
minutes long – with the mean average delay time across all 700+ automated
system failures being just five minutes._

That is _amazing_. Bear in mind that the Victoria Line runs over 30 trains per
hour in the peak! I don't feel that "troublesome" is an appropriate
description.

In the UK at least, a large number of railway routes really are constrained by
the safety margins required for trains. In the late 90s, when the West Coast
Main Line was upgraded, there was an abortive attempt to implement a modern
moving-block signalling system – but it was predictably too difficult for such
a complex line.

I don't doubt that you're right about the incentives being different on low-
traffic lines though. It does demonstrate that there are various benefits to
more automation that need to be traded off against the complexity, cost, and
rust of failures.

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dTal
>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
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)

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mrbabbage
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
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.

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

