What and where is the Northern line extension?
The Northern line extension is a new branch of the Northern line from Kennington. Previously, southbound trains either terminated at Kennington, making use of the Kennington Loop, or continued south to Morden. When the extension opens, the third option will be continuing south in a different direction, along this new branch to Battersea.
Which stations are on the Northern line extension? Have new stations been built?
The existing Kennington station marks the start of the Northern line extension. From here, the line will continue to two new tube stations; Nine Elms, and Battersea Power Station. These two stations have been built from scratch.
Where are the new Northern line extension stations?
The new Nine Elms tube station will be on the corner of Wandsworth Road and Pascal Street. It's already marked on Google Maps (see above), and is close to Covent Garden Flower Market.
Battersea Power Station station (a mouthful of a name which precisely no-one will use — we'll all just end up calling it Battersea station) will be located on Battersea Park Road, close to Pump House Lane and the new Battersea Power Station development. At time of writing, it's marked on Google Maps as 'FLO' (see below), referencing the contractor Ferrovial Agroman Laing O'Rourke which is building the station.
When will the Northern line extension open?
It's expected to open in 2020, and given that the tunnel boring was completed in late 2017, things are on track for that deadline. Stations should be fitted out during 2019 according to TfL's schedule.
Have new tunnels been built for the Northern line extension?
Yes, two new 3.2km long Northern line tunnels have been built between Battersea and Kennington via Nine Elms. As tube tunnels go, they're unique — find out more here.
How frequently will trains run on the Northern line extension?
The specific 'timetable' for the Northern line extension hasn't yet been announced by TfL. But in-the-know tube fans believe that 24 trains an hour will come down the Charing Cross branch of the Northern line, 16 of which will continue to Battersea (the other eight will terminate at Kennington, making use of the Kennington Loop). So you're looking at 16 trains an hour along the extension, which is one every 3-4 minutes.
Will the Northern line extension go to Clapham Junction?
Not initially, no. There has been talk about possibly extending the Northern line extension to Clapham Junction in the future, but don't expect it to happen any time soon. TfL has reportedly said that it's not a viable option unless Crossrail 2 goes ahead — and that's not expected to receive funding until 2022 and won't be built until the 2030s.
What zone does the Northern line extension go to? Will Battersea and Nine Elms stations be zone 1?
Kennington station is currently in zone 2, but when the extension opens, it will be rezoned to a zone 1/2 station.
Nine Elms and Battersea stations will both be zone 1 stations, making them the first stations in the borough of Wandsworth to be in zone 1.
What are the new Northern line extension tunnels like?
They're pretty special actually — the new tunnels built between Kennington and Battersea for the Northern line extension are the widest anywhere on the tube network. The reason for this is that they have walkways built into them, to be used in an emergency. Read more about the new Northern line tunnels.
Will the Northern line extension have new trains?
Despite the fact that the tunnels here are wider than anywhere else on the tube network (see above), the trains won't be any wider. This is because the trains serving the Kennington-Battersea stretch of the Northern line are the same ones used on the rest of the line — lovely as it'd be to get wider trains, they simply wouldn't fit.
Other information about the Northern line extension to Battersea
Trains running northwards from Battersea will only run via Charing Cross — you'll have to change at Kennington for Bank branch Northern line services. Similarly, if you want to get from the Bank branch to Battersea/Nine Elms, you'll have to change at Kennington on your way down.
Find out more about the Northern line extension on the TfL website.