Few topics are as near and dear to me as Shanghai’s world-beating subway system. In the space of nearly a decade in this city, it has made accessible places and people that once felt like an adventurous pain-in-the-neck to visit. That’s progress. Alas, there have long been indications that all this convenience has come at a serious price – in safety. And on Tuesday afternoon those indications became something tangible: human error resulted in a collision that injured more than 270 people on line 10.