Chinese and Indian staff work at a metro car depot of Metro Line 1 in Mumbai, India, June 27, 2018. Mumbai Metro Line 1 became operational on June 8, 2014. The trains, produced by CRRC Nanjing Puzhen Co., Ltd, are designed to be equipped with female-only carriages. All the trains have been in operation for four years without a single malfunction. (Xinhua/Zhang Naijie)