The city of Shenzhen, China, has replaced its entire diesel bus fleet with 16,000 electric buses: the world’s first and largest all-electric fleet. The buses serve Shenzhen’s fast-growing population of 12 million, and have already made a noticeable impact on noise and air pollution; CO2 emissions from public transport are expected to decrease by 48%, as are pollutants like nitrogen oxides, non-methane hydrocarbons and particulate matter. The bus company approximates that 160,000 tonnes of coal per year have been saved and annual CO2 emissions have been reduced by 440,000 tonnes. The bill for fuel has also dropped by 50%. While it is expensive for cities to switch to electric buses, Shenzhen was subsidised by both the central and local government to introduce the new fleet—and much of this financial aid went towards reducing bus fares. The switch has been on the whole successful, in part due to the city’s relatively flat topography and milder winter temperatures.