Great Western Coffee Shop

Good new for commuters, as the GWML is to be wired to support 140mph running, allowing journey times to be slashed across the region. :)

http://www.transportbriefing.co.uk/news/story?id=8664

Hopefully Reading to Swindon will be the first stretch to be upgraded.

_{Sorry, I can't post the article as it's behind one of those pesky password things, I wish they wouldn't do that.}

This is no surprise, the OHLE design is rated higher than this, the route in the 1970's was upgraded in readiness for the HSDT's and the gas turbine APT-E ran many trials at enhanced speed, my guess is very little work will be required.  The major difference will be for maintenance teams access to the line side in the UK where line speed is greater than 125 is restricted to non train periods

And signalling Electric train?

Work will, I assume, be needed on that front.

History tells us that great strides can be made in permanent way and rolling stock, but for some reason the signalling bods fail to keep up.

It won't happen until all the lineside signals have been removed and ERTMS cab signalling controls the trains, scheduled for full implementation by 2025 on the GWML I believe?  I presume the IEP (in electric mode at least) will be capable of 140mph running?  Though there was no mention of that in the recent Government announcement.

If Hitachi can supply a train that is capable of 125mph in normal timetabled running but runs up to 140mph when needed (cf Class 395) then one supposes the same will be true of IEP. Lets not forget, previous and current UK rolling stock, some from as far back as the 1970s (HST, APT-P, Class 91 225, Pendolino) was/is capable of more than 125mph. Other constraints, rather than rolling stock engineering, prevented the greater speeds.

Well it did on the ECML where flashing green signals were installed in 1988 as a trial for 140mph running.
See Section 2.122 lower down the page here http://www.railsigns.co.uk/sect2page7/sect2page7.html
and Figure 8 at the bottom here http://www.railsigns.co.uk/info/aspseq1/aspseq1.html

I'm interested to know why 'flashing green' wasn't taken further at the time. Was it European legislation regarding signalling above 200kph (125mph) or other technical/operational issues here in the UK?

I think it was abandoned as the Class 91 was eventually never authorised to travel above 125mph.

Plus it was deemed that 125mph was the maximum sensible operational speed with trackside signals in Great Britain, hence it won't happen again until ERTMS.

The full ECML electrification was opened for full passenger service in 1991 (if I recall correctly) privatisation loomed in 1994 which took the steam right out of the 140mph project, also there were some (and still are) power supply problems on the ECML which I think was the real reason which privatisation would have stalled the planned changes indeed Cores Mill was not added into the ECML until 2001 and even that was not implement in full and is not due to be until the upgrade to the AT system is done in the next few years.

I thought the problem with the flashing greens was that it was too hard to tell whether they were flashing or not when traveling at high speed. That's just what I've read somewhere.

Also, for 140mph running on GWML, does it really have to wait until the lineside signals are removed? I thought stock that actualy has ETRMS fitted would run with cab signaling as if the lineside signals weren't there, but the lineside signals would be left so trains that don't have ETRMS can still be used.

Common sense suggests to me that with ETRMS fitted trains and lineside signals, trains that are not ETRMS could be run up to 125 m.p.h. (based on sighting the signals) with those with are fitted with the new system where sighting is not required able to run faster.  There's a clear capacity issue on heavily used lines, with each slow train (! if you think 125 is slow) gobbling up several slots between the fast trains ... but that's already a current issue.

That's right - and you have to see the full sequence of the flashing, which takes too long, or might not be pssoible on curves.   Otherwise a green that just failed at the very instant you approached it could be mistaken for a flash off.  I also suspect that a steady green can appear to flash just the same if sighting is affected by fleeting obstructions between the viewer and the signal - such as signal gantries.
Speed up the flashing, and persistence of vision might be a problem, especially with the time taken for a filament lamp to go off and on. (Possibly better with LEDs though)

What about ordinary passengers?   ???

Paul

I'd imagine that the fast lines between Reading and Swindon will only be IEPs though, as XC run on the slows do they not?

Of course, why not have XC running IEPs on the fasts too! ;D

XC do occasionally use the "fast lines" (or main as they are called in GWR land) from Reading but they are limited to, I think, 100mph.  They then turn right just before Didcot Parkway and shortly thereafter the remaining GW services towards Swindon only have a choice of one line in each direction after Foxhall Junction - apart from some lengthy loops in the Challow area.

In 1967 Foxhall Junction was the scene of a derailment where a driver's route knowledge let him down and he made the transition from a four track railway to a two track one at excessive speed and came off the road.

That's exactly what happens on DB on suitable lines. You can watch the driver reprogramme the computer for the LZB fitted sections. A yellow pointer appears on the Speedo to incate the maximum line speed the train can run at, but you still have lineside signals on normal lines.  This allows speeds up to 300kph but not on all lines.

Flashing aspects never seemed very safe to me.  Wouldn't it have been better to add an extra light so "double green" would mean the higher permitted speed.

The problem with that is it is contrary to what happens with double yellow, where the double aspect is a more restrictive aspect than the single, and all the signals on the route would have needed a fifth lamp to provide the new aspect anyway. 

Part of the aim was apparently to avoid new hardware, so that wouldn't have met the requirement.

Likewise a completely new colour was suggested, but this also needed additional hardware, and (I'm fairly sure) the more colours you use, the more problems with colour eyesight standards you get...

Paul

Would they all need a fifth lamp?  With the move to LED signal heads could not the second head (currently used to display the second yellow) also display a second green when required?

Double yellow is not more restrictive than single yellow.

That's right - no idea why I wrote that...  ::)

Paul

They would have needed a fifth lamp at the time of the trial, because LED versions were not yet available - they might not even have been possible - when did reliable colour LEDs start appearing on road trafffic lights for instance?

Portsmouth resignalling used filament lamps, which is only a few years ago, so that perhaps defines when the transition to LEDs on the railway was in progress?

Paul

Years ago, when flashing green signals were first considered, a double green aspect was I believe considered.
It was indeed rejected at the time due to the extra hardware needed, whereas a flashing green simply required an extra circuit to make the existing lamp flash or light steadily.

However as others post, technology moves on and with LED lit signals a double green is easily achieved.
Only four signal lamps would be needed, since each can display several colours.

It would be a relatively simple matter to display
double green
single green
double yellow
single yellow
red

As required.
if the driver failed to to see one of the two green lights that would simply result in a needless reduction in speed from 140 to 125 MPH, say, and would not be a cause of danger.
The double green would be less restrictive than a single green just as a double yellow is less restrictive than a single yellow.

Could it have been an option to have used green and yellow as a new aspect less restrictive than double yellow but more restrictive than green?  This would not have required another light to have been installed.  One issue I can see with this though would have been having two aspects next to each other illuminated at the same time, I'm not sure if that would have been allowed.

Another advantage of LED lit signals is that the brightness of the light may be easily altered so as to be suitable for the conditions.
AFAIK this is not used at present for railway signals*

On high speed lines it would seem desireable to make the signals brighter during bright daylight, in order that the driver may have the best possible view.
In sunlight, the brighter the better, within reason.

Brighter signals have been considered in the past, but have been rejected on the grounds of excessive power usage, and glare at night.

About the present intensity at night, and perhaps twice or more in daylight would improve daylight signal sighting and together with double green signals perhaps allow higher speeds with conventional signalling.

*many road traffic signals DO dim at night, to avoid glare at night but ensure good daytime visability.

Or much simpler on the GWML as it is getting new I/C stock, refurb's stock for TV lines and Crossrail and the GWML signaling is up for renewal to install ETRMS Level 2 so the new trains can run on in the cab signaling and the older trains on line-side

Using the current technology it can be done with only two multi-colour LED heads.
The lower gives red, yellow, or green;  the upper gives yellow or green.

Not all LED installations are the same though, sometimes you do get a separate head for each colour, even with LEDs.

I can still think of other pitfalls not mentioned yet though.  For instance, differentiating visually between single and double yellow at caution speeds is probably not the same as differentiating one or two of the same colour green when running at 140 mph.  Another point which just occured, if your 140 mph section is pretty straight, what happens if at night you can see not just the next signal but a number of others behind it?

All a bit academic now of course...

Paul


  

XC use the fast lines more than occasionally, getting on for half of the time in fact (I think 'Up' Bournemouth's are normally routed on the Main lines, as are the 'Down' Newcastle's), and they are not limited to 100mph and are able to do the full 125mph on that section.

Worth pointing out that in the ITT documents, the Relief lines are to be increased from 100mph to 125mph anyway during the GWML electrification programme:

The Department has asked Network Rail to deliver line speed improvements at the same time as electrification including 125mph on the slow lines between Reading and Didcot.

What about ATP for the XC running at 125?

Is that a recent change?  I haven't caught an XC from Reading for about six months - but in the two years before that I think I only got two or three runs on the main.

What about it?  ATP isn't fitted to Voyagers.


It can vary in each timetable change, but over the last few years I reckon at least one of the four train per hour have routinely been routed on the main lines for most of the day (I've just checked the last 'up' Bournemouth and 'down' Newcastle and they were indeed routed main line.)

What time difference is it? Does the different appear in the TT or is it left as slack?

I thought that all trains travelling at 125mph had to have ATP working on ATP lines. Obviously not.

It doesn't make a significant enough difference to matter as far as the timings are concerned (maybe 60-90 seconds I'd guess?), and Voyagers were restricted to 100mph east of Reading, but no longer work that way. 125mph is authorised between Didcot and Reading.

One of those enduring railway myths?  The ATP section of the online sectional appendix actually includes this:


I'd have thought that might be the case, what with XC Voyagers routinely running at 125 mph elsewhere on the network without ATP.

There are however some specific sections with speed restrictions for Voyagers:


It seems people may have put 2 and 2 together previously, and assumed the speed restriction was a blanket restriction due to lack of ATP, but that doesn't seem to be the case.

Paul

Why are they restricted on these lines. And surely they have never on some of those routes?

All those routes listed would be of use to CrossCountry for diversionary purposes.

Indeed.  When Bristol to Cogload is blocked XC travel via Westbury.  Adds an hour to the journey but better than a bus ;D

I can't see how the two systems would be able to work in tandem without restricting the speed of trains to the lower limit, i.e. conventional trackside signals at 125mph.  Drivers will still need to observe and react to yellow and red lights and I can see ETRMS being very much seen as a background signalling system over the years between its installation and the removal of conventional signalling.  Also, despite the technology being capable of it, I can see a lot of hurdles to overcome before speeds can be increased from 125 to 140mph anyway (level crossings, platforms, curvature etc.).

I'm more inclined to believe the title of this topic "Wired for 140!" than the underlying text.

140 kph I can just about believe.

140 mph though? Not in my lifetime.

Why not - if you ignore all the above diversions about signalling, rolling stock, and ERTMS etc, and although the original post is only quoting a headline from 'Transport Briefing', it is also stated quite clearly in the GW ITT:


That is all they need to do, and from what I've read they are introducing a new OHLE design standard for the GWML and future mainline electrification projects anyway.  There's unlikely to be much of a technological difference between newly installed OHLE designed for 125 mph, and that for 140 mph.  I can't see any major difficulties in dealing with the wiring, to be fair.

Paul 

When approaching a double yellow the target speed could be no higher than 125 mph but I'm not sure this would prevent a higher target speed when there are sufficient clear blocks ahead.

I belevie ETRMS Level 2 allows for this.



It is important to select the right OHL equipment for 140mph running, the Mk3 (never sure if its 3 a, b, c, or d) on the ECML is basically a 125 mph rated design although changing certain components the speed can be increased on plain line and there would have been an increase in the level of maintenance to sustain higher than 125

The following:

http://www.rssb.co.uk/sitecollectiondocuments/pdf/reports/research/T346_summary_rpt_final.pdf

covers the subject with a nice colour map on page 11.

OTC