On November 19, Juche 104(2015) there was a test working for a tube train at night in presence of the respected Comrade Kim Jong Un.
A few days ago he telephoned an official and said that next day he was going to get in a new tube train.
The official told him about the time when the underground traffic is lighter.
He said he was going to get in the tube train at night after service time was over to give no inconvenience to the people.
As a result, the test working was arranged at night when all people went to sleep.