Twelve major cities including London, Paris, Los Angeles and Cape Town have promised to buy only zero-emissions buses from the year 2025.
The cities, with a combined population of almost 80 million, say they will make major areas free of fossil fuel emissions by 2030 to protect the environment.
They would also promote walking, cycling and the use of public transport under a joint “fossil-fuel-free streets declaration”.
Many cities are setting tougher environmental goals to limit air pollution and achieve the goals of the 2015 Paris climate agreement.
Other cities signing up are Copenhagen, Barcelona, Quito, Vancouver, Mexico City, Milan, Seattle and Auckland.