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BR was developing an enhanced version of RETB for use on secondary lines, but that died the death under privatisation. As did the axle counter module for SSI. Likewise talk of Modular Signalling for use on secondary lines seems to have gone quiet.
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It was a master move by SBB as they convinced international committees to adopt their Level 1 LS (limited supervision) concept into the ETCS standards and were able to do an 'overnight' conversion to L1 LS from their recently completed EuroZub and Eurosignum implementations without rewiring anything, 'just' by changing software.
It was probably also in a lot of people's interests to go with that proposal, given Switzerland's location as a small country but on some key north-south routes. Switching to ETCS L1 LS presumably means cabs no longer need to be fitted with Swiss ZUB and Signum systems provided they are already ETCS fitted?
Yes that's still registered as a Class B packet 44 custom system for UK, but has never been used in anger. When the extended fitment of TPWS+ was under development, Railtrack partnered with Siemens in testing an alternative based on this approach. An HST was equipped with the appropriate kit for trials over balises placed around the Slough area.
Please be aware that the "Section C" pages on "The Signal Box" website are not a reliable source of information on upcoming signal box closures. The later pages were indiscriminately based on a Railtrack vision of how a strategic migration of signalling into a handful of Rail Operating Centres might be carried out, but reality has taken a different course.
Brighton Main Line and Three Bridges ASC areas surely makes a lot of sense for ETCS. ASC was opened in the 80's, equipment due to expire within the next 10 years. Easy to move signallers over to TBROC presuming that is where it will be resignalled to. Looks ripe for CP8 I imagine.
Brighton Main Line and Three Bridges ASC areas surely makes a lot of sense for ETCS. ASC was opened in the 80's, equipment due to expire within the next 10 years. Easy to move signallers over to TBROC presuming that is where it will be resignalled to. Looks ripe for CP8 I imagine.
You have a variety of classes (even if they share a common platform) with the electrostars, 66 hauled freight, and the occasional 171 transfers. There's also a lot of branches so there'd be a lot of potential transition points to manage, even if you might be able to get far enough down some of the branches to avoid the nastier ones (e.g. beyond Reigate and/or Lewes).
You have a variety of classes (even if they share a common platform) with the electrostars, 66 hauled freight, and the occasional 171 transfers. There's also a lot of branches so there'd be a lot of potential transition points to manage, even if you might be able to get far enough down some of the branches to avoid the nastier ones (e.g. beyond Reigate and/or Lewes).
Pretty certain its NR's plan to switch the BML to ETCS for CP8. They are not insurmountable though. To me it seems inevitable it will happen. Less variety than on the ECML and that is happening.
Pretty certain its NR's plan to switch the BML to ETCS for CP8. They are not insurmountable though. To me it seems inevitable it will happen. Less variety than on the ECML and that is happening.
Oh it's definitely not insurmountable. Less traction variety but more branches, so there's tradeoffs. It's also one of those areas where having the ability to 'close up' with short block sections at busy stations will be valuable and of course it can function as an extension of the Thameslink ETCS section. Although I'd be surprised if it went all the way from London bridge to Brighton in one go.
Could probably make a nice trial location for a Level 2 hybrid solution if you wanted to do that.
Without freight around it allows an exploration of the operational and economic realities without grasping the thorny issue of what to do about freight.
There's freight still in the area, maybe not so much as there was. I'd still look at replacing any token systems in the area with axle counter based TCB. Asking crew to collect and deposit physical bits of metal from specialist machines in locked cabinets on platforms to ensure safety is utterly anachronistic.... and rather time-consuming.
There's freight still in the area, maybe not so much as there was. I'd still look at replacing any token systems in the area with axle counter based TCB. Asking crew to collect and deposit physical bits of metal from specialist machines in locked cabinets on platforms to ensure safety is utterly anachronistic.... and rather time-consuming.
I worry that buying new conventional signalling installations now has serious implications for the amount of workload on the already overstretched signalling-related industrial base.
There is more stuff to design, install and commission in a conventional installation than one that has no signal heads after all.
I don't suppose there is any possibility of a functional clone of RETB using ETCS hardware?
Geting rid of trackside tokens is probably a high priority, but the staff requirements for Absolute Block may become a serious problem moving forward.
I worry that buying new conventional signalling installations now has serious implications for the amount of workload on the already overstretched signalling-related industrial base.
There is more stuff to design, install and commission in a conventional installation than one that has no signal heads after all.
I don't suppose there is any possibility of a functional clone of RETB using ETCS hardware?
Geting rid of trackside tokens is probably a high priority, but the staff requirements for Absolute Block may become a serious problem moving forward.
In theory it's probably possible, but given that GSM-R connections back to the interlocking reduce the need for large amounts of trackside cable, and that the 'sprung' (hydraulic) points are AIUI no longer permitted in new installations, and that the relative cost of a digital display for the signaller has reduced so that providing a magnetic board might be felt a bit 'old-hat', there doesn't seem to be many advantages of RETB over ETCS L2?
ETCS would provide additional functionality as well, such as MAs being extended or given up without needing to stop, bi-directionally signalled loops, and signalled shunt moves. It also would easily avoid the problem of long-section tokens needing to wait to be released.
In theory it's probably possible, but given that GSM-R connections back to the interlocking reduce the need for large amounts of trackside cable, and that the 'sprung' (hydraulic) points are AIUI no longer permitted in new installations, and that the relative cost of a digital display for the signaller has reduced so that providing a magnetic board might be felt a bit 'old-hat', there doesn't seem to be many advantages of RETB over ETCS L2?
ETCS would provide additional functionality as well, such as MAs being extended or given up without needing to stop, bi-directionally signalled loops, and signalled shunt moves. It also would easily avoid the problem of long-section tokens needing to wait to be released.
The RETB solution allows intermediate blocks without powered systems for train completeness though.
For example you would only need a handful of trackside equipment cabinets for the entirety of the Settle and Carlisle line. You'd need a lot more for "proper" ETCS L2 because you will have a lot of axle counters in the middle of nowhere.
Given the collapse in freight traffic over that line, it'd probably be a good Level 2 "hybrid" test line though.
The RETB solution allows intermediate blocks without powered systems for train completeness though.
For example you would only need a handful of trackside equipment cabinets for the entirety of the Settle and Carlisle line. You'd need a lot more for "proper" ETCS L2 because you will have a lot of axle counters in the middle of nowhere.
Given the collapse in freight traffic over that line, it'd probably be a good Level 2 "hybrid" test line though.
To replicate the AB lengths there today wouldn't require a huge number of axle counters. Cheaper to do it as TCB rather than ETCS though probably. Virtual blocks will have most impact on busy lines where the capacity benefits of shorter blocks are compelling, especially around stations for closing up, and the savings in equipment more substantial.
For example you would only need a handful of trackside equipment cabinets for the entirety of the Settle and Carlisle line. You'd need a lot more for "proper" ETCS L2 because you will have a lot of axle counters in the middle of nowhere.
The S&C isn't going to need a 4 minute headway though. There'd be nothing to stop an ETCS L2 design that was effectively a replication of the existing Intermediate block sections with long axle counter sections - as @MarkyT has mentioned.
It still sees a reasonable amount of freight to the terminals on the line, which is where RETB gets complicated because of the facing points. However I agree that a hybrid system using train-borne integrity detection for plain line and Level 2 around the points would be a possible test plan. Could even trial Level 3 on the Bentham line as part of it.
It still sees a reasonable amount of freight to the terminals on the line, which is where RETB gets complicated because of the facing points. However I agree that a hybrid system using train-borne integrity detection for plain line and Level 2 around the points would be a possible test plan. Could even trial Level 3 on the Bentham line as part of it.
RETB uses ground frames for in-section siding connections in Scotland, as was typical with older physical tokens. Here's how it works:
From Railway Group Standard GK/RT0077 Issue One Date September 2013, Ground Frames and Shunters’ Releases
2.2.3 Release of ground frames on RETB lines
2.2.3.1 Any ground frame operated siding where shutting-in facilities are provided shall be designated as a token exchange point.
2.2.3.2 The electronic token shall only be returned when either:
a) The train is clear of the running line into the sidings and the ground frame has been normalised, or
b) The train has continued its journey under normal token exchange procedures.
2.2.3.3 A ground frame shall be released by an Annetts key. The Annetts key shall be kept in a steel cabinet, on the ground frame, which is fitted with a ‘Castell’ lock. The ground frame Annetts key shall be physically attached to the ground frame cabinet by a chain. The Castell key that opens the cabinet containing the Annetts key shall be physically attached to the CDU (KABA) key, so that it is not possible to release the Annetts key and operate the ground frame without withdrawing the KABA key from the CDU. This prevents the electronic token from being returned when the ground frame is in use.
Note when the GF is normalised and locked allowing the release key to be withdrawn, that process also engages a facing point lock bolt, where necessary (always on a single line carrying passengers), so the points always lie safely lined and locked for moves back and forth along the running line until required to be used to access the siding.
Pros: Safe and secure and not requiring any extra remotely controlled electronic equipment or power on site.
Cons: Time consuming for crew to get down and operate the levers, all the while occupying the block.
The East Suffolk line was an innovative application of RETB on a partially double track line from 1986. It was replaced in 2012 by TCB using axle counters before the start of an hourly service which couldn't be accommodated practically with RETB, probably because the token exchange procedures are too time-consuming.
It was replaced in 2012 by TCB using axle counters before the start of an hourly service which couldn't be accommodated practically with RETB, probably because the token exchange procedures are too time-consuming.
It was replaced because the RETB frequencies were going to be used by Dutch TV (or a phone company, or something). The hourly service was enabled by it.
It was replaced because the RETB frequencies were going to be used by Dutch TV (or a phone company, or something). The hourly service was enabled by it.
The Scottish RETB frequencies were reallocated for use by digital TV channels around Europe in December 2015, driving the "RETB Next Generation" upgrade which delivered new radio infrastructure amongst other improvements.
The Scottish RETB frequencies were reallocated for use by digital TV channels around Europe in December 2015, driving the "RETB Next Generation" upgrade which delivered new radio infrastructure amongst other improvements.
The Scottish RETB frequencies were reallocated for use by digital TV channels around Europe in December 2015, driving the "RETB Next Generation" upgrade which delivered new radio infrastructure amongst other improvements.
According to (ahem!) Wikipedia this system was installed on one 129km rural line in Sweden as a pilot scheme, then intended for some other freight-only applications, but these have been deferred. Sadly the original pilot line lost its passenger service due to the scheme as the operator couldn't afford to adapt the trains to use the system. Italy has trialled the technology more recently.
The ERTMS Regional project was started at the end of the 1990s under the name ETCS LC (Low Cost). In recent years, its development was pushed by the Swedish Rail Administration in cooperation with the UIC organization.
Standardization reached a point in 2009 that the Swedish Rail Administration ordered the equipping of a pilot railway track on the 129-kilometer West Dalarna Line between Malung and Repbäcken in Sweden. Test operation started in 2010, and it has been fully operational (ERTMS only) since February 2012. Unfortunately the high cost of equipping passenger trains with ERTMS caused cancellation of all passenger traffic on this line in 2011.
There were plans to install it on two Swedish freight-only railways in 2012-2013, but that did not happen. The Swedish Rail Administration decided in 2014 not to install ERTMS Regional on any further railway at least before 2020, citing high and uncertain future development cost, risk of problems and lack of expertise, who need to focus on the coming installation on normal ERTMS level 2 on the mainlines.
In 2017 ERTMS Regional trial test runs started in Italy, mainly on the Avezzano-Roccasecca railway [it] line. Rete Ferroviaria Italiana (RFI) plans to introduce this on several low traffic railways.
Haven't there been situations where freight trains have divided but the leak rate is slow enough that the locomotive's compressor is able to overpower the leak and keep the brakes off on a large part of the train?
After all, most signalling systems (absolute block etc) still make provision for determining if a train leaving a section is complete.
Haven't there been situations where freight trains have divided but the leak rate is slow enough that the locomotive's compressor is able to overpower the leak and keep the brakes off on a large part of the train?
I suspect that might be more of a problem in the USA, with their super long consists and multiple locos, than in Europe. They use End Of Train Devices though which plug into the brake pipe on the last car, some of which are radio linked to the cab with a remote controlled brake valve and diagnostics going back. Notionally If the EOTD's position started to vary relative to the cab position more than expected a monitoring system might generate an alarm and perhaps automatically operate brake valves. An electrically triggered brake system with a continuous wire along the train rather than an air pipe would be better, but it makes freight wagons more complex and expensive, as most have no electric equipment on board at all today.
Mostly tail light observation by the signaller. Can be remotely observed via CCTV if the location where confirmation is required is a long way from the signal box, or traincrew can confirm completeness in some systems and locations. 'Train arrived complete' buttons are typically provided for this, in a goods loop situated before the train reaches the signalbox for example.
Edit: Reading up on them (Wikipedia again), modern US EOT devices have two-way communications and display the tail pressure to the driver on the 'Wilma'. Any great discrepancy between the line pressures at the EOT and the lead loco might indicate a split. Some of the latest ones have GPS too.
The end of train device (ETD), sometimes referred to as an EOT, flashing rear-end device (FRED) or sense and braking unit (SBU) is an electronic device mounted on the end of freight trains in replacement of a caboose. They are divided into three categories: "dumb" units, which only provide a visible indication of the rear of the train with a flashing red taillight; "average intelligence" units with a brake pipe pressure gauge; and "smart" units, which send back data to the crew in the locomotive via radio-based telemetry. They originated in North America, and are also used elsewhere in the world, where they may include complete End of Train Air System (ETAS) or Sense and Brake Unit (SBU) devices.
Here's an illustration of the system concept from a instruction and servicing manual for a modern one from Siemens :
document link: https://assets.new.siemens.com/siem...056/obe-00-11-14-d-4-q3920-r3930-q3922-14.pdf
Interesting that it contains the following warning: WARNING THE Q3920, R3930 AND Q3922-14 END-OF-TRAIN (EOT) DEVICES ARE NON-VITAL PRODUCTS. CAUTION MUST BE TAKEN WHEN INTERFACING THE EOT TO ANY VITAL EQUIPMENT AS THE EOT CAN NOT BE USED TO PERFORM, EITHER DIRECTLY OR INDIRECTLY, ANY VITAL FUNCTIONS. ENSURE THAT THE EOT IS INSTALLED PER MANUFACTURER’S INSTRUCTIONS, AND/OR ALL EQUIPMENT INTER-CONNECTIONS ARE IN COMPLIANCE WITH RAILROAD PROCEDURES AND SPECIFICATIONS.
That means you couldn't use it solely and automatically to prove block or junction clearance as the system probably doesn't conform to SIL4, the most rigorous Safety and Integrity Level reserved for the most critical systems, and demanded for anything used in a fundamental way in interlocking.
Notionally, such a device engineered to SIL4 standards might also incorporate an ETCS reader in the EOT that could report to the head that the train had cleared a block or junction. The same functionality might be replicated on passenger trains, most of which are fixed units with cabs at both ends today so could have their rear cab balise reader activated and monitored by the lead cab for this.
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Unfortunately, you can't build portable units as they did with RETB. The system has to be so enmeshed with the traction and braking systems on the host it's just not practical. Remember RETB doesn't provide any train protection. That's why the lines needed a TPWS overlay. Park Signalling Limited developed a module that listens in to the radio token exchange traffic and when it sees the appropriate transaction for the site it triggers an output to de-energise the TPWS track antenna at the stop board while a train departs and flashes a blue indicator to confirm that to the driver. It's almost like a RETB token release for a signal but purists may differ.
Current and Future Enhancements to RETB
Train Protection and Warning System - TPWS
TPWS for RETB was a challenge that was swiftly overcome by Park Signalling. By listening to the RETB token transfer via a Trackside Radio Control Module (TRCM), via a Trackside Radio Control Unit (TRCU) it was possible to determine which token was relevant to which TPWS site.
First installed in 1984, the RETB system was born out of the need to reduce the renewal and operating costs of working lightly trafficked, long single lines found in Scotland, Wales and East Anglia. Figure 2 shows the lines where RETB is installed (and still operating) in Scotland.
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