Where is the safest place in a train?

I have no answer about which car is the safest, back, front or middle, but I am sure that when a car is choosen, the safest seats are the ones that are turned towards the end of the train.

In case of a crash, the train stops brutally and it is far better to have the back of the seat contain you than to get thrown forwards out of your seat.

Based on a look through British accident investigations from the past decade, the safest place is towards (but not at) the rear of the train.

1. Passenger trains tend to derail starting at the front, due to track faults or driving errors (this is in contrast to freight trains, which tend to derail in the middle from suspension or wheel faults). Riding towards the rear means your car is more likely to remain on the tracks, or at least upright, in the event of a derailment.
2. Collisions with debris or vehicles on the track are uncommon, and usually affect the engine or leading car (though there was the one time a cement mixer fell off a bridge onto a train...)
3. Collisions with other trains are vanishingly rare, but because passenger trains tend to run on tracks with a dedicated direction of travel, your train is equally likely to rear-end another or be rear-ended by another.

Overall, in the absence of a rigorous statistical analysis, I'd say that the safest place to ride is the car in front of the rear-most car.

Most rail accidents here (and elsewhere that I'm aware of) involve one train hitting another (slower moving) train front to back, making the back the worst place to be (at least in the train that gets hit :) ).
The safest place then would be right in the center where, whichever you're in (the train that gets hit or the train that starts the collision) you've got the biggest possible crumple zone around you.
Of course there is always the possibility of another train hitting yours right in the middle where you're sitting while your train is running on a malfunctioning switch... Or it runs off an embankment or bridge, pulling the center carriages to crash into a river or lake by sheer momentum.
If you consider everything that can go wrong and assure yourself it will all happen to you, you shouldn't even stay at home as chances of an aircraft or truck crashing into your home are quite real (both happen once in a while), you could even be hit by a meteorite while sleeping in your bed.

The number of carriages would effect my choice. Second or third from last is my starting point, based on having a crumple zone in front and behind me. Also that there is less weight behind me in the probably more likely event of a head on, as opposed to a rear end shunt. Sit toward the front of the carriage in case you get thrown forwards. Sitting facing back seems safest. See what could come flying toward you in the event of a sudden stop. And wear a crash helmet with a red light on top so you can be found.

2. The driver of a vehicle always protects his side unconsciously. I can follow this argument in case of a car, but how should it work in a train?

It wouldn't. There's nothing a train driver can do which would protect the front end of the train at the expense of the back end. The driver's contribution to safety amounts to

1. Observing signals correctly and not driving past one showing stop.

2. Obeying speed restrictions.

3. Being generally observant and reacting promptly if something safety-threatening happens.

Neither of these tasks offers any opportunity to choose between protecting one end of the train or the other. They all contribute to the safety of the entire train and other trains on the network.

i'm curious again about this question!

Unfortunately a train has derailed in my hometown. You can see the graphics at http://elpais.com/elpais/2013/07/25/media/1374703338_483146.html . It's in spanish but the graphic is understandable.

As you see it looks like a derailment because of excessive speed and no additional trains involved. These kind of derailments are the most common IMHO.

Looking at the graphic, it looks like these kind of accidents will follow this pattern: The front wagons derail, and the middle ones get sandwiched by the back ones, that get severely damaged.

The safest places on the train were all the front ones, despite they were the ones originally involved in the derailment.

The worst part in this case was the back of the train.

I wonder what would have happened if the derailing wagon was the back one, if at all possible (it easily can be compensated by the rest of wagons inertia)

UPDATE There's been much much talk lately about this accident in the media, and they have pointed an interesting fact:

• As you see in the photos, where the train derailed there is a wall at the side of the railway. As opposed to uninformed opinions (such as mine), looks like this concrete wall has been a lifesaver, as it helped to keep the train more or less together. If the derailment had been in open field, experts say it would have been much worse, because every wagon would have gone at any random direction, multiple-colliding between each other.

So in my opinion, there's not safest place, because the final fate of every wagon depends on many different things.

The Engineer makes decisions based on extensive training and years of experience but there's is still no decision they could make that would favor one portion of the train or the other. There is however; the lead car, which would be the safest in a pile up derailment situation due to the log pile effect, if you look at pictures of derailments it is plain to see, which is when the cars deflect off opposite sides on impact and stack up like a neatly stacked cord of wood. During this process stored energy is used and if train cars engineering is done effectively many lives will be saved.