There are many Transport for London contracted buses in London, United Kingdom, which operate primarily to serve school children. These buses are usually numbered between 600 - 699 and only run on days when the school which they serve is open. These buses also usually only have between one and three journeys in each direction per day. Trolleybuses, which ran in London from 1931 to 1962, had 3-digit route numbers between 500 and 699, and these included some of the current route numbers used for school buses.