SSR signalling contract to be re-let (again)

Thales were the only bidder this time I believe.

Oh don't mistake me. I have no love for S40 and TBTC, although we are getting some kind of S40+ on the SSR aren't we? I didn't think S40 was up to the job. Not that I expect the improvements to be of ride quality. Actually, the funny thing is, even though Jubilee and Northern line trains spend an absolute age slowing down, they still manage to stop with a jerk - it's quite remarkable, really. I'd describe the ATO on the Jubilee and Northern as childish in its driving style. *Go*. *Stop*. *Go*. I'd describe ATO on the Victoria as downright violent. I hate having to stand on the Vic and I dread to think what it must be like in rush hour.

It will still be S40, but just with the (presumably VOBC software) based upgrades from the Northern line as implied by North End here

I don't mind the victoria line's kamikaze style braking - I don't find it very noticable, and during rush hours, it's not too bad, although those human-sized cushions help! Although experience of riding trams whilst not being able to reach the strap hangers and having to lean into the movements may have helped 

Well we know one big difference is that the SSR system is set to use radio, rather than the inductive loops. An older London Reconnections article cites a press release as saying:


Accompanying the quote with the commentary:


Exactly what that means is not 100% clear, but I think it'll surely have to be more than just the latest, most upgraded version of what's on the Northern and Jubilee.

Ah, I have absolutely no dispute on the motor/brake front, I completely agree and I think it sucks. Also - even just the noise of it is maddening. Well, in terms of keeping speed, yes. But if a Vic line train needs to transition from braking to motoring, I feel it does it quite uncomfortably. And since they slow down quickly and accelerate hard, the effect is quite pronounced. For me personally, I feel jolly tossed around on the Vic line, I don't feel that any thought is spared for gentleness or comfort. The 1992s for instance (for all the Central line's ATO faults), will brake constantly (but hard) towards the stopping mark, and then ease off the brakes in the final few moments for a much softer stop. Whereas the Vic will come in with the motors slowing it down (regenerative braking) and then put the anchors on right at the end. And it feels like a dropped handle. And then they pull away at full whack. And, of course, it's the same when it comes to a stop at a red signal (or equivalent). I read somewhere that sensitive edge was introduced on the 2009 stock because the weight of the doors was enough to pull them open under braking. I know how the poor doors feel!

Judging by the comments about the Jubilee, Northern and Victoria Lines, could it be that despite its age (and naff rolling stock) the Central Line's system offers the smoothest ride and best performance?

As someone who uses that line the most I admit to being biased.

re: slow gentle acceleration and braking, the Overground fits that bill horribly. Its infuriating... surely if the trains were driven with gusto overall journey times could be reduced...

Simon

It isn't just the Central with unreliability. The last journey I did on the Jubilee the train arrived into Canary Wharf eastbound and pulled up about 1½ cars short, the t/op then pulled forward to the stopping mark but it seemingly refused to talk to the PEDs.

Found this article whilst procrastinating. It contains some more details about the system that I hadn't heard of, I certainly found it quite interesting!

www.railengineer.uk/2015/10/15/london-underground-sub-surface-re-signalling/

Last time I checked, Chiltern Trains did not travel down the Wimbledon branch

LU own the infrastructure on the Wimbledon branch, bridges and other structures are numbered into the LU standard system.
Signalling, power control and Rule & Regulations currently remain with NR.
TPWS is already provided on the Wimbledon branch for NR trains.

If I've understood you correctly, I think my interpretation of the information in the link you provided is a little different.

The system, it seems, will indeed use train descriptions to differentiate between LU and NR stock. What the signal will show will, as you rightly say, depend on which train is approaching.

Let's take the example of signals A852 and A854 - the first two automatic signals out of Harrow-on-the-Hill on the northbound main. Remember that the overlap that extends beyond A852 applies to the preceding signal (JB7) and that the overlap beyond A854 applies to A852. (N.B. whether signals, their numbers and their placement will change, I do not know; but let's use the current state of play for an example).

If an NR train is approaching A852 and there is a train between A852 and A854, or in the overlap beyond A854, the signal will be red. If not, it will be yellow, or green. It will be yellow if there is a train between A854 and the next signal (A858), or if there is a train in the overlap beyond the next signal (A858), and green otherwise.

If an LU train is approaching A852 I guess it will be blue under all normal circumstances, as the link says. We might presume it would be red if the movement authority ends at signal A852, but if this is a true underlay, the movement authority should be constantly updated and not forced to artificially end at fixed signals. The system is designed to allow a following distance of around 100 m, with the movement authorities changing to reflect that. (I don't believe it's exactly 100 m, but let's work with that for the sake of discussion.) So unless a train happens to stop exactly 100 m (or whatever the closest following distance is set at) from A852, the movement authority of the following train (if this is a true underlay) will almost never end exactly at A852. If a train happens to be within 100 m of A852, say 90 m from it, then the movement authority of the following train should end 10 m in rear of A852, making a red aspect on A852 unhelpful at best, because although the following train isn't allowed past A852, it isn't actually allowed to approach it either, it should stop 10 m before it. Instead, a blue aspect - essentially meaning 'obey in cab signalling' - is surely less misleading. Of course, colour light signals associated with TBTC can show red, I think the Jubilee has them. But I thought these behaved like semi-autos, where it makes sense for them to be a fixed limit of movement authority.

So, in other words, my interpretation of the information in the link is that the system must determine what type of train is approaching. If LU, it will show blue. If NR, it will show red if there is a train between this signal and the next one, or in the overlap of this signal (which extends beyond the next signal). It will show yellow if not, but there is a train between the next signal and the one after, or in the overlap of the next signal. It will show green otherwise.

Obviously if there's a train in the overlap extending beyond this signal, no NR train will be approaching, since it will necessarily be held at the preceding signal (to which it applies), until the overlap is clear. An LU train may be approaching, in which case, I assume, it will show blue. The movement authority will reflect the exact position of the next train and the movement authority may end in rear of, in advance of, or even precisely at this signal (although the latter is surely unlikely if this is a true underlay).

Of course, I may be completely wrong about this, the link was a little unsatisfying. But this is the interpretation I have of:


And


It would seem a bizarre interpretation of 'underlay' if movement authorities for LU trains were related to fixed, lineside signals. Additionally, if lineside signals do indeed display red aspects for LU trains all the while a train is within 100 m of them (and, hence, no other train would be permitted to proceed past them), this - I think - would be an interesting decision.

If anybody has anything more concrete, or any clarifications, at this early stage - I for one would welcome them

Perhaps it's interesting to note that when TPWS is overlaid on RETB lines a flashing blue aspect was/is used to show that the TPWS loops at the STOP boards were inactive as a Radio Electric Token had been issued for the section in advance.

All this relates to the time before "a train protection system" was mandated by law. When class 165s were purchased for what became Chiltern, they came with tripcocks as a matter of course because that was the system on the Met line over which they operated. At some point once of the BR trial ATP systems was fitted to class 165s this line, but it wasn't applied to the Met.

When TPWS was proposed as the means of complying with the "train protection" regulations, there were four sections of mixed running that needed to be considered. Chiltern, Silverlink to Watford, and Silverlink to Richmond already had trainstops and all the trains that normally used them had tripcocks. Thus nothing was needed although I understand that Railtrack/NR fitted basic TPWS to their sections of track to cover for the occasional visitors. LU dealt with occasional visitors to the Met. by other means (although even the regular rail head treatment train has now been fitted with tripcocks).

LU was left to consider what to do on the Wimbledon Branch. It seemed unreasonable to require SWT to fit tripcocks to its entire fleet (which all had running rights over the section) or to restrict access to the small number of fleets that might routinely access Wimbledon depot (which would then have to have tripcocks). Thus, whilst TPWS was considered to be "less safe" than tripcocks/trainstops, TPWS was the agreed ALARP solution provided it was fitted at every signal, and is what was installed.

In such a situation my layman's understanding is that a driver given such a Movement Authority to pass a red signal is required to "drive on sight" - i.e at a speed slow enough that he can stop in the distance ahead he can see . The "Stop and proceed" rule on the Underground has the same requirement.