This series of trams is systematically equipped to run in pairs.
The photo shows a test drive with recently converted trams. This is the result of an experiment in the recent past. Technically and practically there were no problems, but the trade unions are totally against it, so this problem has to be solved first.
All this is therefore a result of the 2018 trials: https://transphoto.org/photo/1120732/?vid=71760