Transilien double-deck EMU launches new livery
http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/transilien-double-deck-emu-launches-new-livery.html
It's common in RER to see double deck trains. But, the problem of double deck trains is the number of doors. Because of the structural restriction, it's impossible to increase the number of doors.
It means that riding or alighting time of the double deck trains is longer than ordinary trains.
So, RER solved it by widening doors.