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Just when we thought we had written the definitive update on West Coast resignalling, more trouble emerges
Oh what fun we had producing last month's Special Report on the West Coast Route Modernisation. Naturally, we allowed ourselves plenty of time, with my interviews culminating in a tour d'horizon session with General Manager Tony Fletcher on 25 June. Then it emerged that there were to be no meetings until my session with Tony Fletcher.
And Tony was not happy. He wanted to know why Modern Railways was so negative about his project. To which I could only reply that this magazine reports on a fast changing industry and that on signalling in particular, but also on power supplies and possession strategies, there was genuine concern within the industry which Modern Railways has to reflect.
Only after that interview, were we able to talk to other members of the WCRM team, which meant some heavy duty word processor action against the clock, what with Cullen to analyse for this column. Then, as we sat down with a sigh of relief Mr Editor Abbott was told that Railtrack didn't want the special Report published because of ‘commercial sensitivity'.
All this meant that comments on the articles submitted for comment were coming back from Railtrack's press office right up to press day. Which is why I ended up looking uninformed about signalling technology than I was about loco nameplates. So, for the record, North Staffs is not ‘CBI based' but uses SSI, which is what I wrote in the first place only for it to be ‘corrected'.
Meanwhile two new signalling issues have erupted, for both of which the Cullen Report's comments on signal sighting are particularly germane.
First, an editorial in the Newsletter of the Institution of Railway Signal Engineers highlighted what the co-editors called ‘functional inadequacy' in the use of banner repeaters to maintain signal sighting times when the maximum speed on the West Coast Main Line is raised from 110mile/h to 125mile/h in October 2002.
Where curvature or line-side features prevent minimum sighting times from being achieved at the higher speed, one solution is to position a banner repeater at a point before the signal comes into view. A banner repeater has a black bar on an illuminated white disc. The bar replicates the positions of traditional semaphore signals.
When the main signal is at danger, the bar is horizontal – or ‘on'. If the main signal shows a yellow or green aspect the bar is at 45 deg to the horizontal in the ‘off' position.
Many of the banner repeaters you see at the trackside are electro-mechanical, with a bar which moved by a solenoid. However, there are also all-electric versions where the ‘bar' is created by fibre optics or light emitting diodes.
So there you are next Ocober, at the controls of your Class 390 Pendolino, whanging up the WCML and approaching one of the 120 or so signals fitted with banner repeaters. The last signal was green, the banner repeater is ‘off' so what do you expect to see in the reduced sighting time when the signal is in view?
Quite. It could be another green, in which case you keep the power on, or it could be a double yellow, in which case it is power off and start to brake.
Because a two position banner does not differentiate between these two aspects, the driver will have a sub-standard sighting time to read the signal and make a safety critical decision. Indeed, a human factors expert might argue that since the banner repeater read ‘off' the driver might be pre-conditioned to expect a green and disregard the double yellow.
Given the emphasis on signal sighting times and readability in the Cullen Inquiry Report (Informed Sources August), I asked Her Majesty's Railway Inspectorate for their views. They told me ‘ We have yet to receive proposals for the West Coast Main Line Signalling scheme in its entirety. The existing scheme contains a number of sites where banner repeaters are used. Consideration is being given to re-siting the associated signals wherever practicable. Banner repeaters will only be permitted where they are appropriate and within established railway signalling principles criteria.'
Ah yes, ‘established railway signalling principles criteria.' What was it Lord Cullen said in the very first of his 11 Recommendations on Signal Sighting? ‘It should be made clear that the fact that a signal complies with a minimum requirement is not of itself to be taken as meaning that it is adequate'.
It has to be said, that once again Tony Fletcher and his team may come under the cosh because of other people's earlier decisions. According to Informed Sources, the WCRM project team proposed the use of three position repeaters early in the line speed improvement studies but the concept was quashed by the Railtrack Signalling Subject Committee. A three position repeater would have a vertical bar to indicate a green signal ahead.
Meanwhile technology transfer continues to produce headaches at Manchester South. This time, it's the signals themselves.
Ansaldo uses fibre optic technology to give four aspects from two arrays in each head. This is obviously a more compact arrangement than a conventional signal head with a separate double filament light bulb and lens for each aspect.
On Gantry 8 at Ladbroke Grove, for example you would not have need the L shaped configuration of the four aspects, with the red beside the lower yellow (Informed Sources August). And with Railtrack having problems with signal sighting and readability in electrified areas – a gantry had to be moved during the Leeds 1 st resignalling – Ansaldo's four from two could prove handy.
In the Ansaldo signal heads, each optical fibre array can be illuminated by one of two lamps (one for each colour). The top array is Green/Yellow and the bottom Red/Yellow.
Lamp selection is made directly by the interlocking via an electronic control module, the frequency of the power supply determining the aspect. All very 21 st Century, but when a signal sighting panel examined an installation at Manchester South resignalling, concerns were raised over the equipment and its installation.
Concerns included sighting and readability of both platform and gantry mounted signals. The level of luminosity and the narrow focus of the fibre optic signal arrays are also reported to have come in for criticism. According to Informed Sources, the man from the HMRI was quite rude about what he saw, but subsequently a chum in Rose Court would murmur only ‘there were aspects of the signal we were not entirely happy with'.