What do interfaces mean to engineers? Perhaps a good definition would be the interconnection between systems or sub systems from the same or different manufacturers. But this falls way short of listing all interfaces that occur on the railway, many so obvious that we do not recognise them as such.
This was the subject of the recent Railway Engineers Forum seminar held on 2 February in London. Interfaces are a known problem area but could they be managed better if an inter-disciplinary approach were to be adopted?
The seminar sought to gain the benefit of both good and not-so-good experiences of interfaces and to learn how business and other risks can be identified and managed.
Also to probe how ingenious solutions might resolve the more challenging interfaces and examine whether a better understanding at the outset could resolve any problems.
The Wider Interface Realism
An inspired key note speech by Prof Roderick Smith of Imperial College, President of the IMechE and well known for his witty presentations, got to the core of the subject.
Interfaces can be physical, human or system, and are typified by movement, separation, load, friction, energy loss, cost and lubrication. The prime interface of steel wheel on steel rail comes down to diameter, cone and curve. Beyond that comes the interfaces for train movement:
- Driver and signals
- Train on track – quality of ride
- Train and exterior – fuel, drag, emissions
- Signals and catenaries
- On board mechatronics – cab displays, in cab signalling (also in the past steam engine design).
The rail engineering mind will know all this but what about the social interface between systems and people? Many discrepancies emerge in values, interests, knowledge and power. Consider the experience of buying a ticket.
Whilst e-ticketing is encouraged, the casual user often has difficulty with the web site. On encountering a ticket machine, it is invariably at the wrong height, the credit/debit card number requirement is difficult to understand and the fares matrix is bewildering. Apparent high price is off-putting to the casual user which leads to bad press.
Entering a platform requires ticket insertion, usually when one’s hands are full. In Japan, barriers are normally open and read a contactless data card in the pocket. If this is not correct, the barrier will close.
In the station environ, there are too many negative signs – don’t do this, don’t do that. The station may be filled with diesel fumes and noise – is train travel really so green? The condition of the track “four foot” in terminal stations is often disgusting – litter and other unimaginables!
Staff if asked a question, may not know the answer – why do revenue protection people not know train times? A broader knowledge would be so much better.
The advent of high speed rail is welcomed but should be geared to regenerating and bringing together country economic conditions. The supply of electric power will be crucial but how fast should a train go? Surely more important to work out what the journey time should be. HS rail is about mass transit for everyone, not just the rich!
Resolving the interface dilemma should be at the forefront of everyone’s mind. Wherever possible, remove the interface entirely. Not always possible, of course, so remove unnecessary movement, think across the interface, lubricate the interface and understand the system objectives. This set the scene for what was to come.
ERTMS and the Cambrian Trial
the rail engineer has reported on the Cambrian ERTMS trial on three occasions – issues 74 (Dec 2010), 79 (May 2011) and 87 (Jan 2012). Various problems have emerged with the deployed system.
Graham Scott from Interfleet Technology and Peter Leppard, the Operations & Safety Director for Arriva Trains Wales, critically analysed the interface weaknesses that have occurred on this project.
From a TOC perspective, the retro fitting of the Class 158 DMUs proved to be a nightmare. Onboard equipment consisting of DMI, doppler and speed sensors, balise reader and antenna, onboard ATP (sometimes known as the EVC with a SIL4 platform and difficult to change because of safety case approval) tachometer & odometer, GSM-R radio & antenna, juridicial recorder unit plus the inter-vehicle jumpers and a mass of cabling had to be installed on the train.
All were difficult to accommodate on the unit and many proved troublesome when fitted. The train was just not suitable for conversion and it would have been easier (and probably cheaper) to have provided new DMUs with the ERTMS equipment factory fitted.
Operationally, the system is far too restrictive, forcing the Cambrian into a mould of conventional signalling unsuitable for the line. Too much caution is programmed into the braking curve characteristic and it always assumes the worst case.
The effect is cumulative and has actually reduced the number of train paths when the aim was for them to be increased. The speed profiles led to too many short speed restrictions which made the ATP application undriveable.
Cab boot up times are far too long at around 1½ minutes, and the logic processes for the splitting of trains were not properly thought through. Software upgrades take on average eight months to implement. The transmission of axle counter information over the FTN did not have the data formats configured properly.
It is to be hoped that operational as well as technical lessons will be learned, perhaps with a starting point that Railway Group Standards, the ultimate in interface documentation, are not optimal for ERTMS.
The message is – don’t tinker with the existing, start anew. The S&T / T&RS interface needs careful thought; should the on-train equipment be procured by the train builders rather than the signal engineer? After all, it is supposed to be interoperable!
Many platform extensions are currently being progressed to accommodate longer trains with the upsurge in traffic. Sounds straightforward, but many interface complications arise.
Damien Gent is the Programme Manager for the Thameslink 12-car project and gave a fascinating account of the work carried out between London and Bedford. Involving 80% of the stations, the necessary civil works of digging out embankments, driving piles, etc. were obvious tasks.
However, every extension encountered either a signal, overhead line structure, CCTV DOO camera, train stop sign or other encumbrance. Initially attempts were made to build round these but it was quickly realised that the best way was to move / relocate all such items out of the way first, expensive as this was. Building the platform proved to be relatively cheap.
Different standards now exist for platform width which could result in the tactile tiles and yellow lines having a dog leg in them where new met old. This looked odd so wherever possible the new platform would be built to the standards of the old. At Elstree, the use of modular platforms was tried with precast units coming from Germany on a low loader. This proved effective with 140 metres constructed in 24 hours by just 6 people.
Some locations were very difficult. At Luton, the 80 metre northwards extension was constrained by a road bridge that needed three bridge decks to be replaced on a different alignment.
This was micro managed over four days at Easter 2010 with all work timed in 15 minute blocks. It took 13,000 man hours round the clock to complete and included realigning OLE structures and new signals.
At West Hampstead, with its close interchange to both the North London and Jubilee lines, it was recognised that the higher number of people using the station could not enter or exit the platforms quickly enough.
Thus a new footbridge and a second station building were needed to disgorge passengers safely, resulting in a cost of £19 million against an initial budget of £3 million but with much praise being received for the end result.
Fitting Trains to Infrastructure
Obtaining new rolling stock should not normally be a problem with interfaces but when coaches are three metres longer than the previous ones, all sorts of complication can occur.
The Siemens Class 380 trains for the Ayrshire coast were a case in point. George Davidson, the Rolling Stock manager for Transport Scotland and Nick Hortin, the New Trains Director for First Scotrail, described some of the factors that had to be considered.
Before such a project starts, there should be a Train Infrastructure Interface Specification (TIIS), but this was non existent so Siemens with Scotrail designed a compatibility plan. Demonstrating that gauging and stepping were compatible with the existing network meant that the 23 metre long cars had to be 8cm narrower than the earlier 20 metre carriages.
With an improved safety cell and crashworthiness for the driver’s cab, a sloping gangway connection was needed to give an acceptable right hand view. An enhanced automatic selective door opening using GPS and odometry was introduced so as to be independent of ground systems.
Despite testing on the Siemens test track in Germany, in Scotland the AWS receivers were found to be too sensitive and the totally software driven controls (except for the emergency brake) caused problems with driving techniques. As such, the trains were much delayed into service, with consequent delay to the cascade of the Class 334s to the Airdrie – Bathgate line.
Lessons have been learned and for the Edinburgh to Glasgow via Falkirk electrification, a TIIS is being prepared. A Network Rail system integrator will be appointed who will lead the compatibility exercise.
Existing infrastructure constraints, principally at Glasgow Queen St where site restrictions mean the trains cannot be longer, has meant the trains will be 23 metre three-car units. They are expected to be lightweight, energy efficient and capable of 100mph, described as conservatively innovative.
Peter Dearman, the Network Rail Head of Network Electrification, who had given the annual railway lecture to the IET (issue 86, Dec 2011), described the massive programme of electrification being embarked upon; GWML, NW England, EGIP, Trans-Pennine, and five more schemes up for authorisation. Wonderful news, but what are the main interfaces that have to be considered?
- Bridges. Being built too small by the Victorians makes mechanical and electrical clearances a constant problem. Sometimes they can be adapted (soffits attached to the bridge arch) but often a new bridge is required;
- Tunnels. These have similar space constraints but often with the added problem of water ingress. Latest thinking is for a solid aluminium conductor to keep the catenary away from the water flow;
- Grid Supply. A bulk supply is required but feeder points need to be at places where power lines cross the railway. Grid suppliers do not want to distribute large single phase loads. Supplies must also be secure, have the right capacity and be reliable;
- Telecoms. SCADA systems have to give protection and control of short circuits and have to distinguish between these and high loads. Whilst the problem of harmonic induction into copper circuits has diminished with the advent of fibre, immunisation must still be considered. Earthing, bonding and the return path for traction current have to be managed and controlled;
- Stations and Signalling. Earthing and bonding remain important factors that must be understood and managed;
- Trains. Electrical loading and traction system noise are the biggest considerations but pantograph performance is another minefield. The experience of running Eurostar trains on the ECML will be remembered; the ‘Sherman Tank’ design of pantograph with a high upward thrust caused significant problems to the OLE. It is likely the new IEP will have two raised pantographs based upon latest TGV experience on the continent.
Other more obscure interfaces are:
- Gas, water and oil pipelines – great care is needed when excavating for sub stations;
- Power line crossings – enhanced clearances for 11 and 33kV local distribution networks;
- Airports – when runways are adjacent to railways, trip wires are needed to switch off the current;
- Other railways – LUL, Metros when compatibility with third-rail DC and tram power lines is needed;
- Other grid customers – interference from traction system effects, also imported harmonics;
- Public and neighbours – visual impact, earthing / bonding, access to sites and homes.
All these have to be considered, negotiated, planned, implemented and mitigated for any electrification scheme.
London Underground Upgrade Programme
The upgrade of the London Underground Sub Surface Lines (SSL) was reported in issue 85 of the rail engineer (November 2011).
This described many of the interface challenges that existed with old and new signalling and interworking with other lines. Kuldeep Gharatya, the Head of Systems for the Capital Programmes, explained some of the other interfaces that were emerging on both the SSL and the other lines that are currently being upgraded.
His definition “The Whole is Greater than the Sum of its Parts” may be something that all of us should remember. LU is experiencing unprecedented overlapping upgrade programmes and is operating at the edge of the performance envelope.
Separate, and sometimes incompatible, elements within both the internal engineering group and the supply base must work (or be made to work) together. Working in silos does not create reliable and effective end systems. Misunderstanding the interfaces cannot be afforded.
The modern metro is a series of tightly coupled systems – wheel-rail, signalling, train power, power supply, cooling, ventilation, emc, track to train coms, platform-train, ticketing, internet and more. All are software based systems and the complexity has to drive the interface. Even McNulty has said it is essential that interfaces are understood.
The new S Stock trains are the most complex yet. The functional requirements emerged in 3 phases – a brainstorming of need, an indicative design solution, and production of an ITT. Attempts by the signalling engineers to change what was already being supplied were not helpful.
Lessons from the SSL project will be incorporated into a new radical design for the deep tube lines where a whole system programme is being devised for the Waterloo & City, Piccadilly and Bakerloo lines. This will have high levels of automation to give 32 trains per hour capacity. Failing to achieve this will cost huge sums of money.
Altogether a fascinating day and those in attendance should be better informed on the interfaces that can and do occur. There are many more to consider but ignore them at your peril. Engaging all the engineering and operating disciplines at the outset must be the message.