Bank station has two major problems. Firstly it's a very busy interchange, so it gets very crowded down there. In particular the two Northern line platforms are rather narrow and very close together and a persistent bottleneck. And secondly it's a very complicated interchange, which means trekking from one platform to another can take a while. So TfL plan to make the station considerably more complicated, cramming in extra links and passages everywhere possible, and in doing so they hope to greatly ease overcrowding.
• The Northern line's southbound platform will permanently close and a new parallel tunnel will be dug. This might sound radical, but it's a solution that's already been tried successfully up the line at Angel and Euston. In these cases the former platform was knocked through to create considerably more waiting space, whereas at Bank the disused tunnel will become a new parallel concourse. No longer will you have to fight your way along the northbound platform, you'll be able to stroll through the tube where southbound trains used to go. Result.
• A new station entrance/exit will be built in Cannon Street. This'll be a major street-level access, between the Pret on Abchurch Lane and the McDonalds on Nicholas Lane, presumably as part of upcoming office redevelopment. And it'll only be a couple of minutes away from Cannon Street station, providing an alternative route to the District line and mainline rail services.
• Lifts will provide step-free access to the Northern line, from the new ticket hall and from the DLR below.
• A new bank of escalators will be added from the Central line down to Northern line level. It'll head down from the top of one of the spiral staircases, which by the looks of it will disappear. But the foot of the escalator will be some distance from the Northern line platforms, so TfL are planning to install a moving walkway (à la Waterloo) to speed you along the passage. That's a new passage, burrowed inbetween the existing DLR subway and the new southbound tunnel. Told you this was major.
• Want more escalators? Have more escalators. One new set will head down, opposite the end of the moving walkway, as additional access to the DLR. And one new set will head up, from between the Northern line platforms to the brand new exit on Cannon Street. No station in London will be quite so rammed with escalators and moving walkways as Bank/Monument.
If you like 3D cutaway diagrams, it's your lucky day. TfL have producedseveral so you can get your head round what they plan to do. A mighty complex rabbit warren is on the cards, promising faster interchange times via more direct routes and greatly improving capacity. If you like what you see, or if you don't, the consultation runs until 8th November and you should have your say. There'll also be a public exhibition next week at St Mary Abchurch (Tue-Fri, 11am-7pm) where you can see a proper 3D model, watch a film and grill some staff.
If all goes to plan, building work at Bank will commence in April 2016 and be complete by July 2021. Expect a miserable series of closures, diversions and general awkwardness for five years while that's underway. In particular the Northern line will be closed through Bank between April and August 2020 while the station undergoes the peak of its radical transformation. But the end result should be an interchange that's easier and quicker to negotiate, and not a moment too soon.