From Saturday 7 December route 390 will become the fourth in the capital to be served entirely by New Routemasters.
Route 390, which runs 24-hours a day (with N390 services) and is operated by Metroline, runs between Notting Hill Gate and Archway, via Queensway, Lancaster Gate, Marble Arch, Oxford Circus, Tottenham Court Road, Euston, King's Cross and Tufnell Park.
During peak hours, 21 of the new buses will be in passenger service to carry the 18,400 people who travel on the route each day.
Every London bus route is different and as these buses are rolled out across the Capital, Transport for London (TfL) will consider the best possible staffing arrangements on a route by route basis.
Buses on route 390 will operate with the rear door open and a conductor on the rear platform for the majority of the day on weekdays (6am-6pm Monday to Friday).
At weekends this route, in common with routes 9 and 24, will operate with just a driver.
This will mean the rear platform will be closed when the bus is moving but all three sets of doors will be open and closed by the driver at bus stops.
The next route to be converted, the 148 - a 24-hour route - is operated by London United and runs between Camberwell Green and White City, via Elephant and Castle, Parliament Square, Victoria, Hyde Park Corner, Marble Arch, Notting Hill Gate, Holland Park and Shepherd's Bush.
During peak hours, 25 of these state of the art buses will be in passenger service to carry the 22,500 people who travel on the route each day.
The New Routemaster is the greenest diesel electric hybrid bus in the world.
In tests a prototype bus was found to emit a quarter of the NOx (Oxides of Nitrogen) and harmful 'PM' particles of a fleet average hybrid bus and 20 per cent less CO2.
So when all 600 are in service in 2016 they will reduce CO2 emissions in the Capital by around 20,600 tonnes a year.