Signalling on Manchester Metrolink

[Crossover]

Firstly, let me apologise in advance if this ends up turning into a bit of a rant :P

Having recently spent a day on the Metrolink with a few forum people, I got to see the new signalling in action and the bagged over old system.

Now, going back a while, as talk of the Oldham Loop line reopening ensued, I seem to recall that there were tests and teething problems with the new signalling system, which delayed the opening of the line as far as Mumps, initially. I thought this was some "fancy" system but have only now found out that TMS is actually a Line of Sight (LOS) operation, which, to me, seems like a bit of a retrograde step from having "proper" signalling.

Now, I can see that in places, the new signalling has been beneficial, mostly in the city area, especially considering my over-riding memory of Deansgate-Castlefield (or, having been told off for saying it a few weeks ago, GMEX, as it was) was sitting on the bridge waiting for the platform/block circuit to become free is now a distant memory, even if the lack of congestion here has moved congestion elsewhere, we'll let that lie for now...

However, for the 40-50mph running achieved on some of the open areas of line, such as, I believe, the Oldham line, I still struggle to see how it can be entirely failsafe. Can the M5000's stop from full pelt to a stop if they suddenly round a corner to find a tram stopped in front of them? Admittedly, in most places, visibility is very good on the new sections due to the sheer amount of vegetation clearance that took place as part of the conversion, but it'll be back, I'm sure.

It also appears that there are issues with the new system as proven particularly "well" at MediaCity UK - it was so ridiculous it was farcical!
In this instance, we were taking the first tram of the evening to do the curve from MCUK to Broadway. We pulled forward from the right side (as you look at is heading out of MCUK) platform (as an aside, this method of working doesn't half slow the job down and seems to happen on traditionally signalled lines too!) towards the junction signal and we got the middle light, which I am led to believe indicates tram detection. The light then came on, went off, came on, went off and so on. Whilst the driver was speaking to the signaller the tram in the next platform (heading to the city) then pulls forward, gets the light and the route! This then caused chaos as the points were then set wrong further down the line, as trams were now in the wrong order, and prompted the lads in the van to do something. A few minutes later the tram in front, followed by us, now with a route, got underway and we left the tram to double back from Langworthy.

Coming back the other way, we were routed from Broadway and into MCUK without a hitch, then left and pulled forward and got the route out as well (hurrah!). That was about as good as it got though, as we came down the single line section to the triangular junction, this time heading for the system, the signal was "barred" (I think that was the expression I heard from the cab). Looking down the line, it seemed all the points were set for our route across and into Harbour City, all the while one engineer sat in his van, and another having a smoke in a car also parked on the island! After seemingly attempting to contact the signallers on the in-cab system, the issue was eventually resolved when the driver spoke to someone via an (assuming a personal) iPhone!

I can't help but wonder what visitors to the area must think but these issues, alongside the now very uncared for T68's, cannot give a good impression of the system.

Has anyone else seen such things?

I'm expecting starmill may be along fairly shortly

 

[WatcherZero]

Trams have more effective emergency brakes than trains yes because of their expectation of encountering pedestrians and Metrolink have reduced speed limits in some place with poor visibility such as the 'birdcage' the viaduct section between Cornbrook and Deansgate which is visually a curving tunnel.

 

[evoluzione]

As a Man Vic driver, the proper "Birdcage" is actually between Newton Heath and Moston

 

[edwin_m]

The line of sight signalling is not and never can be failsafe. Trams and their drivers need to be able to operate on the street where vehicles and pedestrians can get in the way, so line of sight operation is essential on these sections. On former railway sections the track is much straighter so higher speeds are achievable in safety, although this does indeed rely on vegetation being kept under control.

Knowing some of the people concerned I can assure you that Metrolink pays close attention to ensuring that sightlines are good enough and imposing a speed restriction if they aren't. Incidentally the permitted speeds are based on service braking within the sighting distance, so the emergency brake is held in reserve. Most of the sighting problems actually arise on street rather than former rail sections.

Trams have operated totally on line of sight since the opening of the routes in Blackpool, Sheffield, Croydon and Nottingham and will do so in Edinburgh - it is only Metrolink which has used railway-type signalling. Off the top of my head I can only think of two tram-to-tram collisions where the line of sight operation was a factor.

http://www.raib.gov.uk/latest_news/news_archive/news_archive_2006/060720_pn_new_addington.cfm (tram passed stop signal onto single line, tram in opposite direction did not stop in time, New Addington, Croydon)

http://www.raib.gov.uk/publications/investigation_reports/reports_2007/report172007.cfm (tail end collision, Benson Road, Midland Metro)

 

[Mojo]

http://www.raib.gov.uk/publications/investigation_reports/reports_2007/report172007.cfm (tail end collision, Benson Road, Midland Metro)

Funnily enough I was actually reading this last night; it's quite useful and gives an overview of the ORR guidance for minimum sighting distances, and so on.

 

[radamfi]

Surely there are dozens, if not hundreds of street running tram systems? How many of those use block signalling?

 

[Starmill]

Huh, you don't want to go reading the RAIB report about the Metrolink incident at Piccadilly Gardens last July (in which, someone tragically lost their life) - its full of mistakes!

Crossover and I have discussed this a little already, so I'll be back later with my response

 

[edwin_m]

Huh, you don't want to go reading the RAIB report about the Metrolink incident at Piccadilly Gardens last July (in which, someone tragically lost their life) - its full of mistakes!

Who mentioned Piccadilly Gardens?

 

[Welshman]

Surely, driving Metrolink, or any other tramway system, under "line of sight" conditions, is no more dangerous than driving a bus in service along a trunk road at 45-50mph?

In fact, less so, because on the tramway there's not likely to be other road users doing unexpected things in front of you.

You simply adjust your driving style to suit the conditions appertaining.

 

[Starmill]

Right then, I'll have a go at this. I'm not an engineer by any means, but I do (or did!) know the system quite well and have tried to understand this.

The first thing to recognise is that the existing system was inadequate. It needed to be replaced because the safety attitudes to Light Rail when Metrolink was conceived and developed in the late 80s and early 90s were less permissive - perhaps rightly so through lack of experience with such things - than they are today. Metrolink was a (the?) pioneering second generation tramway. I suspect that the almost direct conversion of the original Altrincham and Bury lines' infrastructure to Metrolink (which we all know was done 'on the cheap' with only minimal modifications to platforms, which leaves us in the rather unenviable rolling stock position of needing high-floor on-street trams, which I don't think is the case anywhere else in the UK) played a part in the decision. I have no idea if any signals, track circuit equipment etc. was re-used, but I know track and other infrastructure was. The bit I meant about the safety attitudes was that apparently 50mph was too fast for a tram and was a bit of 'uncharted territory' for a hybrid system that shared an awful lot of 'heavy rail' characteristics but had very light vehicles. As such Automatic Tram Stop was fitted to prevent SPADs (a bit like TPWS I think) and Vehicle Recognition System (VRS) for tram detection and route setting, alongside mainly two aspect colour light signals, which were either on or off, and some repeaters which showed green if the next signal was off and yellow if it wasn't, all wired up with the Track Circuits.

The original system actually was Line of Sight within the City Centre anyway, how would colour light signals work on the street? The conversion on the Eccles line and in the City (both migrated areas to Tram Management System (or TMS, the new system) was a bit different. In any case, there was some anti-SPAD protection in the form of an ATS beacon at the back of Piccadilly, but this was a white light signal. The Deansgate ramp was until very recently also notorious and the entrance to Victoria Platform C (the current outbound) still is a PITA. Then there was the fact that one of the original manufacturers (or multiple of them, come to think of it, but more to do with the tram equipment and the Italian sheds themselves) had either gone bust or declared the equipment obsolete.

So, what to do? A new system based on Line of Sight was chosen mainly on cost grounds as far as I know. Why provide additional safety protection which isn't necessary? Trams are already driven on LoS principles in Manchester and all over the country. I've heard that the cost is worked out in terms of SEUs (Signalling Equivalent Units?) which were priced at quite a lot for a system running at fairly high speeds and traffic frequencies. TMS requires minimal of these because protection only needs to be provided at points of conflict - merging junctions and merges with road traffic/pedestrian crossings. Orange Points Indicators are provided at most sets of points too. The other problem is one of capacity. Line of sight can support quite a bit more capacity than block-signalled areas because trams can travel practically nose-to-tail, that and the fact that the blocks were far too long in the area around Cornbrook especially, more on that later. I've often thought that perhaps some sort of innovative moving-block system might have been more beneficial... allowing higher speeds by providing more seurity that the road ahead is clear (of other trams, at least) but still allowing trams to travel right behind each other. Who took the decision, when and exactly why I don't know, but I think it was the right one. No other system could provide the capacity required at a reasonable price. As for a safety 'problem'... All of Metrolink's vehicles are limited to 50mph and TMS provides protection at all locations of conflict. The RAIB report about the Piccadilly Gardens incident mentions the deceleration rate of a T68 hazard braking, and I think it was actually more than the industry recommended value in m/s^2 for ensuring that those onboard aren't injured. And that was for a T68 - an M5000 is lighter. I think they are all fitted with magnetic track brakes to achieve this in addition to conventional ones. Finally, TMS offers some other features to help keep the service running as best it can. I think the in-cab screen that seems only to display 'Tram Ready for Service' at the moment is going to be used to allow the driver to monitor how far in front of them the next tram is, and a recommended average speed will be calculated to help keep the service regulated. Variable Message Signs by the track have also been talked of to reduce the need for temporary or permanent speed restrictions at key locations, but none are yet in situ.

The original idea was that the new system, TMS, would be installed across the network before the first extension was due to open in. Of course, for various reasons, most of them technical I think, this was not to be. I'm led to believe that although Thales have had success with similar designs in other countries, retrofitting it onto whatever we had already going here was a nightmare. Unwilling, then, to shut the system down entirely for an undefined period of time to rectify the problem and refit the signalling, with the not-so-small task of convincing Network Rail (who seem to take an age to become convinced of anything safety-wise) that the new system was capable of controlling the Timperley - Altrincham single line section running alongside their own infrastructure and of operating the two level crossings safely (the whole thing, even the trams!!! are currently under 'manual' control from the Deansgate Jn Signal Box I think) to achieve, TfGM pressed on with the openings and some short-term fixes. In 2010, the MediaCityUK branch opened... and what a bloody disaster that was. There were a number of near-misses and almost daily failure and suspension of the line. Exactly why I don't know, but TMS was having problems detecting, routeing trams, and interfacing with whatever the old Line of Sight system was in use on the Eccles line was doing (using VRS, I think...). This is what Crossover has had the 'experience' with, and as such, there is a van parked there during service hours now to deal with any further problems that arise... supposedly.

Then, after MONTHS of delay and immense frustration, the very short spur from Trafford Bar to St Werburgh's Road opened in Summer 2011. This introduced a new Victoria - Werby's service at 5tph, where it still lies, after being extended to Oldham Mumps, then Shaw and Crompton and now to 'Rochdale Railway Station' (awful name). At the other end, the extension to East Didsbury had bought little joy for anyone trying to travel into Manchester through Cornbrook. The Eccles/MediaCity line's little identity crisis didn't help.

Briefly: an extra 5tph were introduced onto the line (thus, through Cornbrook) to MediaCityUK... some of the time. It's complicated when it runs and when it doesn't, and its a little different on Friday and Saturday from what's actually advertised anyway (or used to be) which is a very anti-passenger cocktail, because either your journey takes longer because you have to divert via MediaCityUK, or you everyone has to put up with the delays through Cornbrook. In addition, the contract with Salford Council/Peel (who part financed the line and trams) - TfGM states only 12 minute service between MCUK and Cornbrook. TfGM are sticking to their guns with this one, despite the long unadvertised extension of MC UK trams to Piccadilly. Add to that the fact that it was all broken half the time anyway, and that the harbour City - Pomona section is hellishly slow and you can see why its so hated.

So, whatever the capacity of the block-signalled section around Cornbrook and its Junction actually was, it was far below the 25tph now trying to squash through it. Frankly I wish you'd seen it when it was that bad. Two, or sometimes three waits of 3-5 mins each were the norm. I think we all breathed a sigh of relief when it was converted - and *touch wood* it seems to all be going a bit better now. The number of trams passing through here will rise significantly too after the Victoria and St Peter's Square remodeling is complete, up to 35tph. If the future Port Salford line gets the go-ahead that could be 40tph, or that and Airport line frequency improvement (from 6 min to 12 min, at least in part has been mentioned by TfGM) 45tph. One day Cornbrook might claim a platform which sees the most vehicles per hour in the whole country, stealing the title I believe from somewhere on the Victoria Line (though both operate with considerable differences!).

Metrolink is far from perfect. Some people say its slow and unreliable, and lacks capacity. I dispute the first, defend the second and declare that the third should improve. As I've said to a few of you recently, it will be nice if you can all come back in 3 years to have a look around at the achievements Manchester has made as the largest tram system in the country and the only one to fight back the cancellation of projects. Sadly I'm moving away from my beloved trams in a few weeks and leaving Manchester Since I've stopped commuting on it I already feel out of touch so there are likely to be lots of mistakes in the above! I guess Manchester77 and famillyguy99 will have to keep it up around here

If you made it this far... thanks for reading.
--- old post above --- --- new post below ---

Trams have more effective emergency brakes than trains yes because of their expectation of encountering pedestrians and Metrolink have reduced speed limits in some place with poor visibility such as the 'birdcage' the viaduct section between Cornbrook and Deansgate which is visually a curving tunnel.

As a Man Vic driver, the proper "Birdcage" is actually between Newton Heath and Moston

I'm glad somebody else mentioned 'The Birdcage' before me. Don't want anybody thinking I meant the club.

Its annoying that they have had to reduce the speed limit over there yes :/ But if that means trams can travel closer together (and, of no small significance, two can occupy the platform at the same time! Where else do you get THAT?) then so be it. Overall a very slight journey time improvement has been achieved I'd say. The reliability improvement though is huge.
--- old post above --- --- new post below ---

Who mentioned Piccadilly Gardens?

I did.

 

[edwin_m]

Having been quite involved in the Phase 3 upgrade I agree with the gist of starmill's post though I can't vouch for some of the finer details - in particular a distance to go display in the cab seems improbable and I haven't heard it mentioned by anyone.

The Piccadilly Gardens accident had nothing whatever to do with the replacement of the signalling, which is why I queried its relevance to a signalling discussion. It is on the line of sight section where the TMS now does very much the same thing as the original equipment that was still in place at the time of the accident. The concern was mainly about how the equipment fitted underneath the nose of the tram to prevent someone getting under the wheels probably made things worse.

 

[radamfi]

Thanks to starmill for the detailed and informative post. However, the post uses superlatives in its comparisons with the few other light rail systems in the UK. In a European/world context, is Metrolink really that special? There are numerous other networks involving a mixture of segregated 'pre-metro' and street running.

Obviously the Karlsruhe network is famous and is analogous to Metrolink in having city centre street running and then running on normal railway lines, although this is more of a tram-train. You have the Cologne Stadtbahn which is almost a fully blown underground metro in the city centre but is street running outside. Similarly for the Brussels and Antwerp pre-metros. The RandstadRail in Rotterdam/The Hague even incorporates recent conversions of heavy rail services into tram routes like Metrolink.

 

[edwin_m]

Metrolink is now the UK's biggest tramway but I agree it is not major by European standards. Berlin for example has 600 trams or roughly twice as many as the whole of the UK - and there are almost no trams in the former West Berlin!

 

[Starmill]

I can hardly vouch for my own details at the minute I'm afraid! I'll try and find out what was meant more closely from where I heard about what that orange screen the the M5000 cab is for. I think its used to set the lights, cab air con and heating and a couple of other bits and bobs but I'm sure it is supposed to say something other than 'Tram Ready For Service' the whole time in the long term.

As for how we stack up to the European tramways... well, that just goes to show what the attitude is (or was) like in the UK for innovative transport projects. We might have had more trams, thinking mainly of Liverpool and Leeds, but there were others, were it not for Alistair Darling. Despite the eminent success, particularly of the Altrincham line, Metrolink's expansion was constrained by lack of funding for too long. I agree we have a modest title, and are fairly insignificant on the world stage. Clearly that hasn't simplified the installation of new signalling!

Oh, and the RAIB report I only mentioned for a joke/reference to some figures in it. Yes, the poor chap's loss of life was nowt to do with signalling. :/ That is actually quite a clever unsignaled merge (reduced complexity = money saved) with a 'give way' sign on one road so the points can be trailed from both directions, which is safe because both run parallel to each other for a good distance before merging. All the same, 'H' diamonds have now been added there to ensure horns are used.

 

[edwin_m]

I think it's a bit unfair to blame Alastair Darling for the lack of trams. We've had a stop-go (but mainly stop) policy towards them ever since the 30s. Even with Leeds, Liverpool and South Hampshire we'd still be nowhere in the tram stakes compared with the Germans etc (who developed most of their tramway post-war instead of closing them) and even the French and Spanish (who closed most of theirs but then had a big change of heart.

In Nottingham the display shows "tram ready for service" or something similar, except when there is a fault to report, which most commonly seems to be a flange lubricator fault with which the tram can continue in service.

 

[Crossover]

Thanks for all the responses, especially starmill for their in-depth one

When you mention about the "Tram ready for service screen" possibly being used for some other reason, this is what I had expected with the new signalling system, to be honest, especially given the problems they had on the Oldham Loop.

Maybe I should have been a little more specific and less sweeping about TMS - in the city, as has been pointed out, LoS has been in operation for some time, and is indeed the only way to go about doing things, and it has made improvements on in other areas, like the approach to Deansgate...even if it has shifted congestion onto elsewhere. Having the ability to get two trams into a platform at a time (if singles) is also a benefit, though where doubles are concerned, I'm sure some members of the public will never grasp the concept that the whole thing has to be platformed before a release is given :P

What seemed most surprising though was the use of LoS on the high speed sections. There was a point, rounding a corner somewhere round Oldham Mumps (I think it may have been between there and Rochdale) and I have to wonder that, if a tram was stopped on the line ahead, if a driver could react and stop in time before rear ending it, especially from some of the higher speeds.

Are there are any other tram systems than run so fast on LoS signalling?

 

[edwin_m]

Yes, Croydon does 80km/h on LoS. Nottingham is 75km/h max and not sure about the others.

 

[Crossover]

Yes, Croydon does 80km/h on LoS. Nottingham is 75km/h max and not sure about the others.

Maybe I'm underestimating the braking capabilities of a tram somewhat :P