Although it looks as if the era of fossil-fuel powered cars has peaked, it will still be a number of years until these cars are off our roadways completely, with 2050 being estimated as the year electric cars take over for good. But there’s one type of conventional vehicle that is phasing out much faster: the bus.

The humble municipal bus is on the vanguard of the electric evolution. In fact, the head of transport for BloombergNEF estimates almost 70 percent of the world’s buses will be electric by 2040. That compares to just under 40% for all other types of vehicles. Electric buses, like many fleet-owned and commercial vehicles, make a compelling business case. While the sticker price for an EV is generally higher than conventional vehicles, the total cost of ownership—upfront price plus fuel, maintenance, and other costs—is already lower in some cases. New York City, for example, said this year electric cars in its fleet are already its least expensive option.

And while America has slowly started to embrace electric buses, China has made electric buses a priority. Two cities—Guangzhou and Shenzhen—have converted their entire municipal bus fleet to electric. Shenzen’s 16,359 electric buses outnumber the entire bus fleet of New York, Toronto, Los Angeles, and Chicago combined.