 London Transport had instigated a Bus Reshaping Plan in 1966 to examine bus service operation, and settled on replacing some double-decker buses with long single-decker buses, which would have extra capacity by implementing a 'standee bus' model as used on the continent, whereby the fixed seating in the bus would be minimised to that required off-peak, with hand holds fitted to allow maximum standee capacity at peak times.These buses would also have dual doors.The concept was introduced with on 18 April 1966 with six AEC Merlin buses on a new express service, route 500, running between Victoria and Marble Arch, extended during shopping hours to Oxford Circus.