Leon Daniels, Transport for London’s MD of surface transport, told the Assembly Transport Committee that eight prototypes would have to undergo “thousands” of miles of testing before an order could be placed for a full fleet.
The prototypes are planned to be on the streets by next spring, weeks before the Mayoral elections.
Their performance will then dictate any modifications which need to be made to the vehicles ahead of full production.
Disability campaigners say the bus offers insufficient space to wheelchair users.
The new bus was a 2008 manifesto commitment by Johnson who held an open competition to develop the design but the Mayor has faced criticism for spending £8m on the project while implementing a series of fares increases.
The test vehicle is the result of collaboration between Wrightbus, Transport for London and the Heatherwick Studio.
Like its famous predecessor, the new London bus will have a rear platform for boarding, however this will be closed at certain times of the day.
