It was only a few years ago that a lot of the Bank branch was closed while the new platforms were built at Bank right? I'm surprised they need to long term engineering work so soon. It does seem sensible to me to do it Monday-Thursday evenings though
The previous closure was Moorgate to Kennington, so that didn’t cover the whole section. I know at least one section being done this time is KX to Angel SB.
A few thoughts on this. Generally LU does surface track renewal during weekend closures, and this tends to include the sub surface lines as well. Tube track replacement by contrast tends to be done overnight. I’m not sure if this is simply because Tube lines are generally busier and therefore it’s to reduce disruption, or whether logistically it just works better. Not all replacement is the same, as in some cases the underlying support structure will be renewed, at other times it’s literally just the rails changed. Due to its history as being an older line, parts of the Northern Line have less usual support structures, such as concrete between the sleepers, which presumably will require more work then elsewhere.
My suspicion is this is about cost. On a normal night you will only get a couple of hours useful work, as the engineering hours window is essentially 4 hours which also includes having to set up and clear away. By extending the time it allows a full shift of work, which is likely what is being paid for anyway, so in theory it would reduce the number of shifts required for the full programme of work, so producing a cost saving.
I doubt this method would be used elsewhere, as it’s likely been chosen for the Northern because of the two branches, so it’s fairly easy to implement. The other alternative is weekend closures, which people would probably dislike.
