

Innovation in rail travel: The train that never stops at a station - bensummers
http://www.youtube.com/watch?v=p9Ig19gYP9o

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thingie
Hardly an innovation. Various people already had the same idea so many times.
It seems quite an obvious and tempting thing to do.

[http://blog.modernmechanix.com/2008/12/18/train-picks-up-
and...](http://blog.modernmechanix.com/2008/12/18/train-picks-up-and-drops-
passengers-without-stopping/)

Well. It's pretty much unworkable. Train is not a single rigid body, it's
composed from bogies and car bodies, and they are only quite loosely attached.
They absolutely have to be. So you can't expect it to just sit as a rock on
the tracks, even in pretty low speeds. And with speed low enough, you are
maybe better to simply stop. Modern electric bullet train unit with high
powered axles ratio can accelerate really, really fast.

Anyway, you could spend money much better on allowing higher speeds on the
whole track, or improving adjacent tracks so to allow higher speeds even for
feeders and conventional trains, which could allow you to make fewer stops.

~~~
stcredzero
_Modern electric bullet train unit with high powered axles ratio can
accelerate really, really fast._

Yes, but accelerating the entire train is going to cost way more energy than
accelerating the transfer car. Also, the transfer car can simply use wheels
and brakes to gain kinetic energy from the train, so it can be incredibly
light. Even if a longer track and motor are necessary for high speed bullet
trains, there would still be a big energy savings.

Also, no matter how quickly you can accelerate to make a stop quickly, the
same train will be able to save considerable trip time with the transfer car
system. Saving a half hour or hour off of trip time from a route is certainly
worthwhile, especially if it means that the train can run the same route at a
lower top speed. The energy savings from that could be enormous over the long
term.

~~~
wheels
I'd also thought of this independently in the past, presumably lots of people
have. As for decelerating, I have no idea if any modern trains do this, but
you could in theory charge a battery with the kinetic energy from decelerating
the train and use that for acceleration. Naturally it wouldn't be a perfect
energy transfer, but I presume much of it could be captured.

~~~
quant18
<http://en.wikipedia.org/wiki/Regenerative_brake>

Seems like it's everywhere these days. Even in urban metro lines where you've
got like 1km between stations. HK subway trains have been doing this since the
90s. Wikipedia sez Delhi Metro has it too.

~~~
thingie
It's most useful in such cases (and trams and so on), with very frequent
braking and starts and a lot of trains. There is always some other train
accelerating. And you have majority (if not all) axles powered, so you can
have regenerative brake on all of them, allowing you to brake effectively only
with the regenerative brake to almost zero. It's even much more silent than a
mechanical brake, also an advantage in urban environment :-)

(And even if you don't give the energy back to the network and just burn it in
the resistors in locomotive, it gives you more effective braking. Locomotives
from 1960's already had that.)

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asimjalis
Implementing the idea and making it work safely would be quite innovative. I
can see a lot of things going wrong.

* What if the door on the pick-up car gets blocked? Sometimes straggling passengers hold the door open for their friends. It would need to get out of the way to prevent a collision with the drop-off car.

* What if there is a malfunction in the pick-up car so that it is not able to accelerate fast enough to catch up with the train?

* From an engineering point of view this seems fragile -- there are a lot of parts that need to perfectly synchronize with each other. A single error will quickly cascade through the system and result in serious loss of life.

~~~
hxa7241
Yes, and weighing the whole thing against alternatives makes it questionable.

First, it might save lots of energy, but it is also a lot more complicated
than just having brakes, which it is going to have anyway.

And how much energy would it really save? It still has to accelerate that
detachable portion which could be a substantial fraction of the whole, and
furthermore the train would probably need to be substantially heavier to
support the extra mechanism, which would be a loss . . .

Still, it is a creative leap, which makes one think about how to be similarly
inventive. You have to get some wild ideas before figuring out the details.

~~~
RiderOfGiraffes
It saves a lot of energy. Accelerating one part can be done by taking energy
from the incoming sub/super carriage. Accelerating and decellerating the
smaller carriages is much more efficient than the whole train.

~~~
krschultz
Are you sure? How much extra air drag will there be having a hump that
basically doubles the frontal area and adds a load of form drag?

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hugh3
How's this for a simpler implementation without many of the problems which
have been mentioned:

Approaching the station, there's an announcement on the train "Everybody
getting off at the next station please move to the last carriage". Then the
last carriage simply detaches from the train and coasts into the station to
unload at the platform.

Meanwhile, another carriage has been loaded with the passengers who were due
to get on at the station. After the train passes the carriage is shunted by a
small locomotive to catch up with the train and it attaches to the end.

No need for crazy long parallel tracks and dangerous transfers between high-
speed trains. Difficulty: most high-speed trains have locomotives at both ends
afaik, but that's a minor issue.

~~~
thingie
High speed trains don't have any locomotives (only German ICE1 uses this
approach), powered axles (and other electric equipment) are distributed across
the whole unit. (So you can't split it, only couple/uncouple two units
together.)

But, if you think that those transfers are dangerous, I don't know what to say
about coupling in high speeds. Insane, maybe :-) Coupling even in station when
only the locomotive is moving is favorite source of accidents. Basically you'd
have to reach almost same speed as the train you are coupling with in the
exactly same moment when you are going to touch it, with only very small
difference that buffers can absorb. Hard enough if that speed is zero.

~~~
extension
Surely the trains would be specially constructed to perform this procedure
reliably, and it would be entirely automated. This doesn't seem like it should
be a hard problem if the system is engineered from the beginning to handle it.

~~~
thingie
Coupling two things together in 200 or 300 kph is not a hard problem? That's
like people without any programming experience saying, hey, that traveling
salesman can be easily solved for 10 nodes, so just add more power and solve
it for 100 or 1000, that cannot be that hard!

It's quite hard to control exact speed of a train (at such high speed), even
without any atmospheric effects and with ideal adhesion conditions that never
change. I can imagine it in like 50 kph, when the worst thing to expect is a
derailment, some deformation zones blasted, and few non-fatal wounds. But
every problem rises at least exponentially with the speed.

~~~
hugh3
Fair enough, I hadn't realised how difficult it was to control the exact speed
of a train at high speed.

But if that's the case then it still seems like the original problem of
running two trains right alongside each other, on different tracks, for
several minutes while people cross from one to another, and with the
consequence of any error being passengers getting sliced in half, would be
even harder.

------
hussong
Version with explanation in English:
<http://www.youtube.com/watch?v=K27VmNfwsaQ>

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JulianMorrison
Hah, I invented something like this in my head for amusement, except mine used
swappable modular carriage pods that plugged into the train from the side, and
a steam catapult for high-gee synchronization and emplacement. I can't see a
sensible use for it though.

~~~
nooneelse
I just figured that half the kids watching Knight Rider back in the day
thought of a similar trick using cars and trains... I know it was a day dream
of mine for a while.

~~~
JulianMorrison
It would certainly help if the car in question was robot-controlled and could
jump several meters vertically without a ramp.

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_delirium
Here's a brief post about this video from a few years ago:
[http://www.goodcleantech.com/2008/07/futuristic_train_lets_p...](http://www.goodcleantech.com/2008/07/futuristic_train_lets_passenge.php)

~~~
hussong
I'm still wondering what the docking looks like. Somehow people need to get
from the connector cabin to the train and back. This could also result in a
lot of people moving back and forth within the train over 20 stops if you can
only get in and out at the back of it.

~~~
andrewtj
The route mentioned in the video has 30 stops over a distance of ~2200 km so
it's unlikely there'd be much congestion. Stops here in Australia are even
sparser over those sorts of distances so it'd work quite well here too.

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vaksel
pretty cool...kinda sad that the U.S. stopped doing cool things like this.
What was the last big infrastructure project?

~~~
hugh3
Remember that big infrastructure projects are a lot easier in China since the
government has no hesitation about demolishing entire villages which might sit
in the way of the latest highway, rail line or dam.

~~~
rbranson
O?
[http://en.wikipedia.org/wiki/File:Chongqing_yangjiaping_2007...](http://en.wikipedia.org/wiki/File:Chongqing_yangjiaping_2007.jpg)

~~~
nanotone
That's an extreme example. How many people are going to fight to keep their
home after having power and water cut and a 30-foot pit dug around it?

Keep in mind that on the whole, Chinese people are much more likely to give up
personal property/liberty for the benefit of the state. It's a massive
generalization of course, but the difference between Chinese and American
mindsets is really significant.

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pierrefar
Looks cool as a concept but I'd like to see an actual implementation.

Also, the initial jolt on impact of the pick-up car is going to be very
unpleasant, and perhaps even dangerous.

