Why does it affect other lines?

[Deleted]

Recently while reading on TFL i noticed when something goes on (e.g. East of Aldgate East) It affects trains in Central London (Circle, Metropolitan lines). Why is this?

[Deleted]

I'd guess that if for instance all Hammersmith and City and half the District trains are turned at Whitechapel, there would be blocking back, with Circles and Mets being jammed between the H+C and District trains. And also AIUI with the new Circle timetable, trains do both Circles and Hammersmith and City trips on the same day. If the (ex-H+C) trains aren't at Hammersmith when they should, they aren't in time for their Circle trip.

[citysig]

That's more or less it in a nutshell.

Whilst a failure on a non-Met part of the city should not "in theory" impact on the line, trains being delayed to/from the failure area can also then end up delaying Met trains within the city area.

We do try our best to avoid other lines becoming involved - because at the end of the day it's more mess for us to clear up - but sometimes it is unavoidable.

The combined timetable does mean that H&C trains going on to form Circle services may be delayed and vice-versa, but this is not simply a problem with the new timetable. Before the change, both lines could easily suffer from a problem unrelated to either line - and could also take much longer to recover.

[Colin]

And it's because of the unique interaction between all of the SSR lines that this very board was created.