Side note:

With lessons learnt, "the construction of future lines will be increasingly easier, faster, and more cost-efficient", Hoang told AFP.

Hell, yes! Line 2 took ages and was embarrassingly late. (Slated for 2010 opening, it finally limped across the finish line in late 2012, IIRC, and had major teething problems, including one train catching fire, thankfully at a terminal station with almost nobody on it. The next five lines were up in a couple of years, and the remaining half dozen seemed to spring up out of nowhere, not to mention the constant extensions of existing lines. Twelve years, eleven new lines, plus countless extensions. It unfurls like magic once you have the techniques and challenges down.