The Zone 2 station is crucial in making sure the Northern line smoothly takes passengers from various branches to one another. What made the line a success may soon be its demise.
The Northern line is incredibly complex. Serving extensively Central London including both the tourist destinations of Leicester and Trafalgar Square and the financial district of the City of London, it is one of the busiest lines on the network (in 2016/17, it surpassed the Central line) and it is no surprise given its reach. Only a couple of years ago, an extension from Kennington to Battersea Power Station opened giving the Northern line another endpoint and a 7th* branch and Wandsworth Council are actively considering extending the line from Battersea to Clapham Junction, Europe's most intensely served train station. The line could be destined for a surge in passenger ridership but, at the present moment, the existing infrastructure simply could not cope in this scenario.
To add capacity to cope with ridership demands, TfL had actively been pushing for the Northern line to split into two pre-pandemic: trains running to Morden would run exclusively via Bank and Battersea-bound trains would run via Charing Cross. There had been conflicting reports about whether the line would also split the Edgware and High Barnet branches but the push for a Northern line split was encouraged as both branches would be able to run 32 to 36 trains per hour as opposed to the 24 to 30 trains per hour by avoiding the current situation at Camden Town Junctions.
Camden Town is arguably the biggest obstacle facing the Northern line - it is rather the crux of the issue. It is often compared to its southern counterpart Kennington but Camden Town is far more crucial and busier. Not only does Camden Town get severely congested because of nearby tourist attractions (Camden Market and Camden Lock), it is a major interchange for Northern line trains. Trains from Edgware and High Barnet meet here and then proceed to either the Bank or Charing Cross branch - all done via the Camden Town Junctions. The Camden Town Junctions are unique in that the frequency of the Northern line means that more trains pass through these junctions than anywhere else in the country. It is these junctions, however, that limits the amount of trains that can pass through.
By separating the Northern line into two, trains would not be limited by the points at the junctions (therefore allowing more trains to pass through safely). Problem solved? Not exactly. Should the line be separated, then Camden Town would become a major interchange between the two lines - the same would apply to Kennington. Camden Town would need a major station upgrade - an upgrade that would significantly disrupt local area traffic given that the station sits at the meeting point of the Kentish Town Road and Camden High Street. Proposed by TfL, the station would have a second entrance, step-free access and a new central concourse, effectively tripling the size of the station.
Unfortunately, given the difficult financial situation TfL is in, there has been no further progress on the station upgrade. First delayed because of Crossrail and now because of financial constraints, the station upgrade is on indefinite hiatus - some very disappointing news given that 97% of respondents in a 2018 consultation showed support for the upgrade plans.
Where does that leave the Northern line? As mentioned before, Camden Town lies at the heart of the Northern line's solutions (and problems). With its upgrade put on hold, the Northern line is further away from the split proposal and therefore its capacity can't increase. Can we avoid an interchange at Camden Town? It is possible given that Mornington Crescent is a 10 minute walk and is already exclusively served by Charing Cross trains but this would not solve the interchange problem. By getting rid of an interchange, passengers would have to change at Euston. Euston is already congested because of the interchange with the Victoria line and National Rail services from Euston Main Line - it is set to be even more congested because of the future HS2 terminus. Therefore, Euston Tube station would need significant upgrades to cope with the additional interchange traffic from Camden Town - an upgrade that could cost considerably more given its location within Zone 1 and Central London.
Passenger numbers will continue to rise and the Northern line is operating to near full capacity - as mentioned in a previous post, TfL's eagerness for cost-cutting but temporary solutions are understandable but does not help in the long run - inevitably, it will harm the growth potential of the Northern line, the Tube and even London as a whole.
* the 7 branches are considered Edgware, High Barnet, Mill Hill East, via Charing Cross, via Bank, Morden and Battersea Power Station