Sorting out the SSLs

Something like this was proposed once, but it was shot down because it would have resulted in greater pressure on the flat junctions on the Circle Line. Given modern, neoconservative thinking on signal overlaps and interlocking, you probably wouldn't be able to handle the increase in traffic over the junctions unless you did some judicious resignalling.

The Circle does technically have a terminus - Aldgate, the one place they have exclusive platforms in both directions. Circle line trains technically have 'recovery time' built into the timetable - so if it's all running to time, you will often sit at Aldgate for five minutes or so, waiting correct time to depart.

Ugh.

I presume then that something will be done about the increase in tph over Praed Street Junction?

Which will result in a theoretical service drop between HSK and Paddington Praed Street.

I assume that the theoretical loss in service levels will be balanced by the increased reliability of the services that are still running?

The ideal would probably be to get rid of the Circle entirely, thus eliminating many of the conflicts at flat junctions. It hasn't really served much useful purpose since the District trains were extended from High St Ken to Edgware Rd around 1930. LT wanted to get rid of it in the 1930s, but decided it was legally obliged to run the service.

When redesigning the SSL service, there are a few things that have to be kept in mind:-
1) The capacity through Earl's Court (remembering that it is a driver depot).
2) The capacity through the various flat junctions.
3) A service pattern that is the same on all lines (e.g repeats itself every 8.5mins, as opposed to being 7mins on one line, 8 on another, and 10 on other).
4) Maintaining service levels on all parts of the SSLs (many plans seem to reduce the HSK-Paddington service).



Going back to the Tea Cup/Praed Street Junction/Edgware Rd issue. The junction capacity would be increased from approx 22.5-30tph (in all directions). This is still considerably lower than other flat junctions on the SSLs such as Baker Street which handles approx 54tph (in all directions). Also, taking in account there is no door closing time added to the equation at Praed Street, then it should be able to handle the increased traffic. Edgware Rd would have to reverse twice the number of trains, increased to approx 15tph. But, again as long as stepping back is in place, then again in theory this shouldn't be a problem.

On the Aldgate issue, I believe that there is about 5 mins timetabled dwell time there for Circles. If the same amount of catch up time was applied at a terminus without stepping back in place, then the train would have to dwell for 9 mins. No which one is the most efficient use of stock and drivers?

that's ok.

surely t-cup line diagrams already exist (pretty much) as c-stock have all c-stock lines on their line diagram.

but from what i understand of your posts, the service will be hammersmith-edgware rd-kings x-tower hill-embankment-edgware rd/wimbledon.

one question remains - pink or yellow?

Hi James, welcome
Most of the stuff discussed here is in connection with the replacement of A, C & D stock, by the new S stock - so stock numbers are not necessarily relevant.

The H & C service to Barking would most likely be replaced by the Metropolitan line.

As for the Rayners Lane Branch, it's still only a rumour at this stage, but does seem very likely to happen.

Did the met one include the Croxley link?