That's also a possible factor in why those sitting in the rear half of the plane during a crash are more likely to survive - they have the front of the plane as the crumple zone.

Although for trains, it looks like the middle might be the safest (in case of a rear-end collision).

Well actually. Trains are designed now to not have "telescoping" crashes. If you think the trains being sturdy doesn't lead to a reduction in loss of life in these collisions.. Well it could be much, much worse.

I'm not familiar with all the safety features in design now, but there are quite a few. I wouldn't be surprised if they are designed to deflect and derail during collision now.