The New Circle

It's got to be given a go, that's for sure, although the whole concept is flawed. I was at Edgware Road last week and the two island platforms do not seem wide enough to cope with the large numbers of people that will transfer between them. But we need to try it to poove it doesn't work.

At the end of the day, the current system needs to be addressed and modifed to get the best out of what we have, and sadly the T-cup option does not include this!

I'm not so sure, having spent part of the evening looking *very* carefully at the previous c. 18 months timetable notices.

I've noticed that the only really new thing about the 'Extended Circle' is that it has been badged and packaged up as that.

Bits of it have been running on odd occasions for a while; I may be totally wrong here, but my suspicion has been confirmed by looking through some Thameslink-related and Farringdon/KingsCrossish timetable notices (I stress this is only a guess on my behalf, nothing more) and quite a few elements of the service pattern have already been run - you know *sneakily* . Tested. In service. Who noticed? Who complained? ;D ;D

Obviously I can't comment on the staffing levels/rostering as I'm not privy to that sort of information, but going back through the records I've got to hand, I wager that most of the service has already been proved in parts. What needs to be proved is that all the elements stick together and work.

As a timetable afficionado I hope it does, as it is quite an elegant bit of planning. Now; can the TDs be sorted?

It is what will happen in the interregnum that will make life for the operators interesting..........

I was thinking the same. Keep the TD for the signalling equipment the same. Is it possible to change the DMI so that it says (at Embankment westbound for instance), Edgware Road via Paddington.

So does the TD Code go into the DMI which translates it for customers? Or is it done before?

There is a fair bit of in-built recovery, but this is only good for "normal" run of the mill late-running. Have a decent shutdown at say, Hammersmith or on the south side of the Circle and you lose both H&C and Circle services at once. You still have the trains, but limited options of where to put them - which isn't so different from today. But we will have to be continuously aware that what action we take on the Circle at one time, will affect what happens on the H&C in the near future.

Today, if we need to suspend the Circle, on one side or the other, those 7 trains are sent somewhere - Farringdon sidings, Edgware Road sidings and Hammersmith depot. Job done. When the shutdown is over, the 7 are brought back in from each of those locations.

From December, if we need to lose one side of the Circle, it will be an ongoing task to keep trains away from that area. Plus, if we turn trains short and return them in the opposite direction, we have to also keep in mind that gaps will now occur in the un-related service later on if you see what I mean.



The SCC computer receives each TD from Tower Hill as the correct destination - that is Upminster / Barking / Dagenham / Circle rather than just District / Circle. Tower Hill cannot send an eastbound "Hammersmith" TD for obvious reasons.

The TD displayed at Aldgate is taken from the trip edit - but the code is for Aldgate site as a whole. There is no facility to split the area as far as TDs go, for example to have "Approaching Aldgate" moving to "Aldgate Station." If this was possible, then the old "Circle" TD could show for "Approaching Aldgate" with it programmed to change to "Hammersmith" at "Aldgate Station."

When the new timetable comes in, it will be as it is now late evening. Trains bound for Hammersmith will be sent as, then allocate as Circle. Then when they move to Liverpool Street the next line of the trip edit can then change the TD to Hammersmith.

It can be done manually at Aldgate, but this requires constant intervention from the operator - and the system is neither designed nor set up to operate in such a manner.

This is where the spare / unused capacity could be used. Perhaps the current "Aldgate East" TD for the Eastbound could be used. This could be sent from Tower Hill, changing automatically to "Hammersmith" at Aldgate.

Yeah, same as the Heathrow area nowadays.

I was wondering how the DMI (in old fashioned lands) translated the TD Code. Such as SC staff see (for example) a ABC code as 'B', the DMI shows Barking. I'm wandering where the programming for the Barking bit is. Is it in the DMI itself or in the Tx or Rx TD units? If anyone can make sense of what I've just said!

AIUI, TD are, manually or by computer, set up as serial data, then Rx automagically converts it to parallel data; Tx transmits as serial again.

Parallel data stored as the destination. Recieved and transmitted data filtered, synchronised and stored.

In the TD units; rather than the DMI would be my outside guess.

And if another part of the database of much confusion is to be believed; this has always been the case since September 1960 when Parsons Green and Putney Bridge were automated with supervision from Earls Court; the same codes were extended as programme machine working crept westwards - looking at First Supp. to TC40/60 and associated.

How curious that decisions made half-a-century ago still have the capacity to affect the system!

Oh why didn't you say. Of course, without the old Decimal blah blah Octal twing twang... it's all perfectly clear now ;D

Some interesting future changes regarding destination protocols have emerged recently –

Trains starting from Hammersmith will be described as “Circle Line via Aldgate” instead of “Circle Line via Kings Cross” or “Circle Line via Liverpool Street”. At Aldgate this will change to “Circle Line to Edgware Road”. In-car DVAs are to be amended to match.

On the return trip trains will be described as “Circle Line via Aldgate”, then at Aldgate change to “Circle Line to Hammersmith” with “Hammersmith” shown on station DMIs.

Revised station line diagrams will be installed on stations to reflect the new pattern of service once its permanence is confirmed (though I thought the latter was non-negotiable!)

On S Stock there will be two lines of destination text on the cab LCD display allowing both destination and line name to be shown.

There is also a proposal to amend the existing C Stock destination blind to include the revised descriptions.

Between myself and a couple of colleagues, we threw a couple of additional bricketts onto the New Circle BBQ. (Well with the current "summer" you have to have one somewhere ;D )

First off, a key manager's question to me reminded me of a little problem in terms of Traction Current in the Hammersmith area. The line between Shepherds Bush and Hammersmith is single-end fed from the Shepherds Bush end. Too many trains on either road, and the current will trip out on over-load. To the best of my memory from when I was a signalman at Hammersmith, this was more than 3 trains on either side - in particular on the eastbound.

Now how many times, during bits of late-running, is this going to happen? A couple of times a day never used to matter that much. In fact as a signalman it was almost a celebration that you must be doing something right in shifting trains from Hammersmith, if you got the juice to trip-out. But I wonder what will happen if the circuit breakers are constantly tripping out, all day long.

The other matter was how the service will operate once the S-stock has arrived.

The Edgware Road area is to be re-signalled (again) to take account of the new trains. Basically, you won't be able to bring any train into the middle roads if there is a train on either outside road with the station starter off. You also won't be able to signal a train into the middle roads until a train leaving Edgware Road in the same direction has fully cleared the overlap of the station starter.

So for example, a reversing train following a through eastbound won't be able to be signalled into the station until that train has its rear end beyond the pointwork to the east of the station.

On top of this, it is not known how the increased length of the trains will be accomodated. The original length of the platforms is obviously longer than at present, but then if this is utilised the signalling in the area will have to be altered even more simply to satisfy current signalling standards with regards to overlaps etc.

And even once all this is done, will a 7-car train be able to fit and reverse in the middle at Edgware Road. Let us not forget, reversing at Edgware Road is a bit of an important bit of the new timetable ;D

Something somewhere in what you've said doesn't quite make sense to me; however, I'm sure that you are perfectly correct. Why can't the approach - well, the Outer Homes signals (what are currently OP 1 and OP 36) have their controls modified to turn them into 'crawler' signals down to OP 2/3 or OP 33/34/35? Now I might be missing something quite obvious here (including the possible need for a derogation from LUL signalling principles) - but I cannot see a difference in principle between OP 1/36 being converted to something like the following signals on the Jubilee:

• TH 186/100 Westminster
  
• TJ 158/TJ 100; TJ 157/TJ 800 London Bridge
  
• TL 118/TL 100 Canary Wharf
  
• TM 114/TM 100; TM 115 TM 2000 N. Greenwich.
  

Now, I've not looked in particularly strict detail at these, but the sequence of [TLX 123 RTL 125/RTL 1100], [TL 125/TL 1100] at North Greenwich seems appropriate.

From what you've written, I get the clear impression that successive movements across Praed St will take anything up to ½ - 1¾ minutes longer than currently timetabled (this is only a rough guesstimate and thinking about track circuit occupancy in advance) - if so this is surely quite a retrograde step. OK, some of the extra time could be clawed back by trimming the terminal allowance at Hammersmith from 12 min as stands at present (IIRC the first Circle and Hammersmith WTT from 1989 was generally an 8 minute terminal allowance) [1]- but how thin can you shave the allowances??



Indeed, and picking up on Chris M's point, part of the problem is the mix of electrical and mechanical interlocking at Edgware Road. I'm pretty sure looking at my notes that the locking isn't that different from when the frame was first installed. Now, overlay relay locking on top of mechanical locking isn't technically impossible, but it adds another layer of complication and a greater need to use all the contact bands driven off the lever so both sides of the interlocking (mech. vs relay) will 'know' where everything is.

I'm sure that when the all-singing-and-dancing new signalling is installed then these problems can be addressed quite straightforwardly through carefully looking at target speeds on the approach. The nub of the matter is getting old kit to work with the new timetable (and allowing graceful degradation when it all goes chest-uppermost).

[1] the H&C transit times and platform allowances are of particular and special relevance to what goes on at Edgware Road, and it makes interesting reading (well, to me at least) how things have changed over the years, I can go back 103 years on this particular set of data!

The last re-signalling altered all sorts, including the provision of speed controlled signals in place of those which weren't before if you see what I mean.

OP36 and OP2/3 were two of the signals altered to speed-controlled signals. Their alteration (as well as that of OP4 and OP31 on the approaches) was deemed sufficient at the time to provide adequate protection, alongside the additional alterations to the locking.

Not knowing how things are costed etc. but which would be cheaper? Altering a signal to speed control, giving it this condition and that condition, or altering the same signal to simply not clear until the preceding train is at point X.

Much of what is handed to us, is, unfortunately not always based on the best option, but the cheapest / simplest option.

Remembering, of course, that one of the big selling points of the new timetable is that increased recovery at Hammersmith. It is planned (by management at least) to be one of the saving graces of the timetable, and indeed it is also the main reason why we cannot have self-contained Circle or H&C services.

Mind you, this is all a couple of years off, and we haven't had the timetable in yet. But it would make a mockery of the reasons behind getting the timetable in its current form introduced.