There are 3,773 hybrid buses, 316 electric buses, and two hydrogen buses operating in London, as of March 2020, out of a total bus fleet of 9,102. This had increased to 450 zero emissions buses in March 2021, and due to become 750 buses by the end of 2021. The city has the second-largest electric bus fleet in Europe after Moscow, which has over 500 electric buses operating. The first hybrid bus was introduced on route 360 in 2006 and over 300 were in passenger service by July 2012. The world's first double-decker hybrid bus was introduced in London from January 2007, and the world's first double-decker electric bus in 2015. As of 2021, Transport for London plans for all buses in London to be zero emissions by 2037, although according to the Mayor of London this could be brought forward to