Late 2016, London Mayor Sadiq Khan announced to join 11 other major cities, including New York, Los Angeles, Copenhagen, Hamburg and Amsterdam, that have committed to begin moves to phase out their procurement of pure diesel buses by the end of 2020. With the initiative, major cities are working together to challenge bus manufacturers to produce more zero-emission buses and make cleaner bus technology less expensive. Together, these cities have committed to procuring 1,000 zero-emission buses using either electric or hydrogen technology over the next five years. In London, a 51-strong fleet of all-electric buses (BYD), and in Eindhoven, the Netherlands, a 43-strong fleet of all-electric buses (VDL) have started operation by the end of 2016. These initiatives are leading examples of scaling-up from proof of concept to large-scale operation of zero-emission bus transport