TIMES ARE tough for Tesla. Lately sales of the firm’s pricey electric vehicles (EVs) have fallen around the world. Yet in Bangladeshi cities, a humbler namesake is flourishing. Battery-powered rickshaws—jokingly named “Bangla Teslas” by locals—are upending urban transport. The guess is that there are now more than 4m (up from 200,000 in 2016), transporting tens of millions of people every day. They are perhaps the world’s biggest informal EV fleet.