One thing I noticed upon moving to Germany is the fact that people seem slightly obsessed with saving energy. Personally, I find the automatic shut-off of the lights on my staircase slightly annoying. And I cannot imagine that it saves that much energy. In any case, the point is that I was actually kind of impressed with the subway doors in Berlin. In most cities I have been to when the subway stops, then all the doors open at once - and you just go in whichever one you feel like.
So why? (Because obviously it must be more expensive to install these doors - what with their sensors and lights etc.) My guesses are as follows:
1. It takes more energy to open all the doors, and generally, other than at rush hour, passengers will not require all the doors to open.
2. In the winter time fewer open doors means less cold air entering the UBahn/SBahn, which means that it will take less energy to keep the the train warm.
3. Germans like things like that - it "feels" efficient.
