In the Northern Hemisphere at this time of year, the leaf fall season has traditionally posed major problems for railways, and it exposes the crucial interface between train operation and infrastructure for all to see.
The slippery properties of compressed leaf mulch on railheads are well known and – these days – understood. The primary risk is undoubtedly a train losing adhesion as it brakes for a signal check and passing the signal at danger and out of control. But another more insidious problem occurs when a buildup of mulch insulates the rails and prevents track circuits from operating effectively. This can give rise to trains disappearing from signalling displays or simply not registering that they have passed a signal. The failsafe nature of signalling – that a train is not allowed into a section ahead unless it can be proved to be clear – means that mishaps are unlikely, but it adds another potential headache for rail operators.
Thankfully, with the problems well understood, the solutions seem to be working well this year with few indications of undue delay: a combination of defensive driving techniques, water cannons clearing railheads and proprietary solutions applied to rails are gradually defeating the problems caused by leaf fall. Increasing replacement of track circuits with axle counters is also undoubtedly having an effect in improving the reliability and consistency of train detection.
Sceptics may suggest that the obvious solution is to chop down all trees near operational railways but ownership and conservation issues make this a non-starter in most countries. The reality is that a combination of proactive infrastructure management to limit the causes and rapid reactive measures to target known ‘hotspots’ is the best most railways can hope for. On the evidence so far this year they appear to be doing a good job.
Ensuring that train consists remain intact is a cornerstone of signalling. Accidents have happened (and doubtless will continue to do so) when trains split unintentionally – but for signalling engineers across the rail industry, providing the planned radio based, moving block ERTMS Level 3 system with sufficiently robust train integrity measures is proving a real headache.
Years ago it was simple – tail lights on the last vehicle of a train would prove to a lineside signaller that the train was intact and that the preceding section could be cleared. Track circuits and axle counters provide the same functionality for today’s centralised control centres. But how do you prove a train is intact when there are no fixed block sections and no lineside infrastructure?
In theory, when a train splits accidentally, brakes are automatically applied and the vehicles come to a stand, usually not too far away from each other. But no signalling designer in the world would rely on that for ERTMS Level 3: the old axiom that anything that can go wrong will applies particularly to signalling – who would really guarantee that all the vehicles in a formation would come to a halt relatively close to each other? And what if an unbraked train (perhaps a failed high-speed train being towed to a depot) splits? How could ERTMS Level 3 deal with it?
Perhaps we need to look at radio transponders on each vehicle that communicate with the control centre – any significant variation in speed between vehicles in a consist would be spotted and the appropriate alerts given. That would be viciously expensive though, and what about freight trains that are marshalled en route? Could there be some sort of ERTMS ‘tail light’ that provides confirmation that the end of the train is where it’s supposed to be? As with tail lights on existing trains, how could relocating the equipment to the rearmost vehicle be guaranteed?
These are all questions that are going to have to be answered before ERTMS Level 3, with its potential for absolutely maximising route capacity, can go forward with confidence. To judge from the experience of railway history, a solution will be found and it will probably be conceptually very simple. The question is – with sufficiently intelligent design, can ERTMS Level 2 deliver most of the benefits of Level 3 without introducing yet another layer of complexity to a signalling system which is beginning to match the expectations of its designers? Perhaps the exhibits at InnoTrans in Berlin will shed some light on this fundamental issue…
With less than four weeks until the end of the year, two major new signalling and train control announcements have been made in Germany and South Africa.
DB is inviting tenders for the equipment of ICE1 power cars with onboard ETCS equipment. Credit: DB
Deutsche Bahn – a railway whose enthusiasm for European Train Control System has been rather muted compared with its neighbours – is inviting tenders to fit ETCS onboard equipment to 80 ICE1 Electric Multiple Unit power cars with a potential option for a further 38 to be fitted. Although DB’s use of ETCS is relatively small, the ICE1s operate extensively to Switzerland and Austria, which are both rolling out the signalling system nationally.
Siemens, meanwhile, is to install new signalling and train control systems in the Gauteng region of South Africa in a €180 million contract to be finished by 2018. Having already installed up to date signalling on a quarter of the Gauteng network, it will now install 83 Trackguard Sicas S7 interlockings, Clearguard ACM 200 axle counting equipment, and a track vacancy detection system to determine whether track sections are clear. It’s the latest in a series of South African deals for Siemens, which has also won contracts from Transnet Freight Rail to upgrade the 860km Orex iron-ore line with Trackguard Sicas S7 interlockings.