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Is there any particular reason why third rail hasn't been looked at as an option for some of the more costly and difficult electrification projects, such as MML, North TPE and Hope Valley?
I know the trains would need a pantograph and a shoe as they would also use overhead wire sections, but why is it not being used for TPE when it works well in the South East?
Despite being a Southern man at heart, does it really work well anywhere? It may have once been attractive because of the limits of early twentieth century technology and low initial cost, but now OHL electrification is likely to be more efficient (I leave others to define efficient). Even if cold winters are going to be a thing of the past, especially in the south, there are plenty of ways where the third rail is regarded as unacceptably dangerous nowadays.
Is there any particular reason why third rail hasn't been looked at as an option for some of the more costly and difficult electrification projects, such as MML, North TPE and Hope Valley?
I know the trains would need a pantograph and a shoe as they would also use overhead wire sections, but why is it not being used for TPE when it works well in the South East?
I seriously don't see any of the three examples in your first sentence being considered for third rail just because of power limitations and existent OHLE being connected to them partially or with through services using them. If third rail was ever to be reintroduced in new electrification projects it would most likely be infills in between third rail areas, such as the Marshlink, North Downs and Uckfield lines. However the main talking points for those is battery power potential rather than full electrification of any form.
Any completely new Tube line, if one was to be built (I'm not counting Crossrail), would not be third rail unless it was, like the DLR, shielded bottom or side-contact third rail. In limited situations, extensions of existing third rail can be allowed.
Any completely new Tube line, if one was to be built (I'm not counting Crossrail), would not be third rail unless it was, like the DLR, shielded bottom or side-contact third rail. In limited situations, extensions of existing third rail can be allowed.
Any completely new Tube line, if one was to be built (I'm not counting Crossrail), would not be third rail unless it was, like the DLR, shielded bottom or side-contact third rail. In limited situations, extensions of existing third rail can be allowed.
Who says? Often quoted is the Electricity at Work Regulations 1989, but the Jubilee Line extended as new work from Canning Town to Stratford 10 years later in 1999 with no issue, and with the conductor rails just a few feet from where people stand on the platform. More recently the Central Line at Stratford opened a second westbound platform where passengers step directly across the live rail on that side almost immediately below. It seems these new works are all OK in the regulations with the conductor rails in far closer proximity than NR third rails, but a normal fenced rural line is somehow not.
Is there any particular reason why third rail hasn't been looked at as an option for some of the more costly and difficult electrification projects, such as MML, North TPE and Hope Valley?
I know the trains would need a pantograph and a shoe as they would also use overhead wire sections, but why is it not being used for TPE when it works well in the South East?
As already pointed out, it's less efficient and more dangerous, but more importantly no more reliable than OLE and would also severely limit performance with it's 100mph max speed and massive power restrictions. Hope valley would be the only vaguely acceptable line for third rail from those you've listed
Who says? Often quoted is the Electricity at Work Regulations 1989, but the Jubilee Line extended as new work from Canning Town to Stratford 10 years later in 1999 with no issue, and with the conductor rails just a few feet from where people stand on the platform. More recently the Central Line at Stratford opened a second westbound platform where passengers step directly across the live rail on that side almost immediately below. It seems these new works are all OK in the regulations with the conductor rails in far closer proximity than NR third rails, but a normal fenced rural line is somehow not.
It's pragmatism - There's no way of fitting OLE to a tube gauge train whilst leaving passenger accommodation that is usable. Having two different shoe pickup systems is also a non-starter and effectively forcing the 4th rail system. There are no such 'mitigating circumstances' that force you to only use a third rail on the hypothetical rural fenced line
Plainly we are not likely to see third rail outside the existing areas but did I not see hints that a somewhat more liberal view of fill in schemes was on the cards? It does seem awfully restrictive to rule 3rd rail out for, say, Marshlink (though of course that is 25kV OHLE at one end! Bad example perhaps.)
It's not the law, but the ORR has claimed that's what the law means. I wish the politicians would tell them otherwise, but that seems unlikely, so it'd probably take a scheme backer willing to fund a judicial review.
It's not the law, but the ORR has claimed that's what the law means. I wish the politicians would tell them otherwise, but that seems unlikely, so it'd probably take a scheme backer willing to fund a judicial review.
Far cheaper to add Third Rail new on that stretch when you consider the amount of tunnels to the south of Whitechapel which probably couldn't take overheads, particularly the Thames Tunnel. Clearances to turn Whitechapel (LO) platforms into a AC/DC changeover zone were probably also a limiting factor - Farringdon doesn't have another set of tracks going overhead.
It is an engineering choice about (amongst other things) how to comply with the law. It may not be 'reasonably practicable' to do something different for a minor extension. It is patently not 'reasonably practicable' to re-bore the entire underground to fit OLE. It would normally be 'reasonably practicable' to avoid using third rail to electrify a line between OLE areas. You may not think that the ORRs interpretation of 'reasonably practicable' is law, but good luck with that in court.
The problem is on what "sensibly avoided" means. As the debacle over bridge clearances has shown, the ORR's notion of sensibility is not shared by many across the industry.
One certainly gets the impression with ORR Standards is that their interpretation depends very much on who is in their office on the day. Engineers are normally quite capable of working to what is reasonably practicable and what is sensibly avoided. the trouble with these vague concepts is that they leave one open to being second-guessed by a politically (small p) oriented organisation which one day happens to have someone in place who wants to Make a Point one way or the other.
Far cheaper to add Third Rail new on that stretch when you consider the amount of tunnels to the south of Whitechapel which probably couldn't take overheads, particularly the Thames Tunnel. Clearances to turn Whitechapel (LO) platforms into a AC/DC changeover zone were probably also a limiting factor - Farringdon doesn't have another set of tracks going overhead.
This also means that there won't be any track workers on the line except when train movements have been stopped, at which time the power can also be shut off removing one of the hazards. There's probably less likelihood of trespass too than on an open-air railway.
Third rail makes sense for metros and similar railways and is still used for new ones today, although as mentioned it would be bottom contact unless extending an existing route. These probably also don't allow staff on the track while trains are running, and with closely-spaced stops the extra weight of a transformer for 25kV operation probably outweighs the power loss in the third rail and return. For a longer-distance railway the economics favour a higher voltage, as much less of the power is wasted in resistance losses and the power feeder stations, while larger, can be much further apart.
Third rail makes sense for metros and similar railways and is still used for new ones today, although as mentioned it would be bottom contact unless extending an existing route. These probably also don't allow staff on the track while trains are running, and with closely-spaced stops the extra weight of a transformer for 25kV operation probably outweighs the power loss in the third rail and return. For a longer-distance railway the economics favour a higher voltage, as much less of the power is wasted in resistance losses and the power feeder stations, while larger, can be much further apart.
It is possible to fit fibreglass shielding troughs around top-contact third rail, and it rather surprises me that this hasn't been required to be done more widely, particularly on extensions, as while it would do nothing to prevent an idiot standing on it, it would certainly reduce the risk of a member of staff who should be stepping over it brushing it with clothing or similar. Does anyone know why this hasn't been done? Is it to do with the possibility for e.g. leaves to clog it, perhaps?
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Third rail makes sense for metros and similar railways and is still used for new ones today, although as mentioned it would be bottom contact unless extending an existing route. These probably also don't allow staff on the track while trains are running, and with closely-spaced stops the extra weight of a transformer for 25kV operation probably outweighs the power loss in the third rail and return. For a longer-distance railway the economics favour a higher voltage, as much less of the power is wasted in resistance losses and the power feeder stations, while larger, can be much further apart.
Don't forget, though, that you can use low-voltage OHLE, as trams do - for an entirely new-build light-rail metro installation I would be favouring that. Indeed, I think what I would do for a completely new metro is basically build an underground tramway using off the shelf tramway components and vehicles - cheaper and more options for the future.
There's not, I suppose, all that much difference (other than age and where they run) between a Newcastle Metro vehicle (which are possibly the most German-looking things in the UK), a DLR vehicle (other than the power being third rail) and a Metrolink tram.
It is possible to fit fibreglass shielding troughs around top-contact third rail, and it rather surprises me that this hasn't been required to be done more widely, particularly on extensions, as while it would do nothing to prevent an idiot standing on it, it would certainly reduce the risk of a member of staff who should be stepping over it brushing it with clothing or similar. Does anyone know why this hasn't been done? Is it to do with the possibility for e.g. leaves to clog it, perhaps?
It's done in some areas where staff are more likely to be present, such as depots. Possibly with more widespread use in less frequented areas the hazard to staff fitting it (from general trackside working, as the third rail would be isolated) would be greater than the lives saved by future contact avoided.
Don't forget, though, that you can use low-voltage OHLE, as trams do - for an entirely new-build light-rail metro installation I would be favouring that. Indeed, I think what I would do for a completely new metro is basically build an underground tramway using off the shelf tramway components and vehicles - cheaper and more options for the future.
There's not, I suppose, all that much difference (other than age and where they run) between a Newcastle Metro vehicle (which are possibly the most German-looking things in the UK), a DLR vehicle (other than the power being third rail) and a Metrolink tram.
You can, but third rail tends to be the default choice for light and heavy metros with no street running. The bottom contact third rails are mostly made of aluminium I think, which has a resistivity only about 65% more than copper. With a larger cross-section, an aluminium third rail would have less resistance than the same length of copper OLE, so the third rail solution has less energy loss in an equivalent application. This is particularly significant for long heavy metro trains with a higher current draw. For underground metros third rail also reduces the tunnel cross-section.
To be pedantic the Metrolink (and Croydon) trams are probably the most German-looking things in the UK, as they are minor variations on designs supplied to Cologne.
Isnt Crossrail basically a new tube line Ok they decided to connect it to the mainline network which made it a no brainer for overhead electrification and standard loading gauge, but as has already been said any new totally new underground line would likely be similar to Crossrail with overhead electrification and standard gauge. Obviously for an extension to the deep tube underground using anything but third rail would be impractical, but for main network getting more third rail past the extremely risk averse ORR good luck with that.
Is there any particular reason why third rail hasn't been looked at as an option for some of the more costly and difficult electrification projects, such as MML, North TPE and Hope Valley?
I know the trains would need a pantograph and a shoe as they would also use overhead wire sections, but why is it not being used for TPE when it works well in the South East?
Who says? Often quoted is the Electricity at Work Regulations 1989, but the Jubilee Line extended as new work from Canning Town to Stratford 10 years later in 1999 with no issue, and with the conductor rails just a few feet from where people stand on the platform. More recently the Central Line at Stratford opened a second westbound platform where passengers step directly across the live rail on that side almost immediately below. It seems these new works are all OK in the regulations with the conductor rails in far closer proximity than NR third rails, but a normal fenced rural line is somehow not.
I think that the outer contact rail in 4th rail territory is at the same alignment as the SR 3rd rail. 3rd rail units share the Wimbledon - East Putney line with LUL, don't they.
Pat
It is possible to fit fibreglass shielding troughs around top-contact third rail, and it rather surprises me that this hasn't been required to be done more widely, particularly on extensions, as while it would do nothing to prevent an idiot standing on it, it would certainly reduce the risk of a member of staff who should be stepping over it brushing it with clothing or similar. Does anyone know why this hasn't been done? Is it to do with the possibility for e.g. leaves to clog it, perhaps?
Short Circuit Bars are not to be used in areas where there are kickboards/shrouding, so I guess to have them across the third rail network would remove the ability to use SCBs to get an immediate current isolation in the event of an emergency, as well as being an extra thing to have to maintainand inspect or become dislodged. I suppose a kickboard that was mounted in such a way as the bottom of it rested slightly higher than the bottom of the conductor rail might still allow a SCB to be used though. As @edwin_m says, areas where there is regular footfall, such as depots and sidings, do generally have kickboards in place.
One certainly gets the impression with ORR Standards is that their interpretation depends very much on who is in their office on the day. Engineers are normally quite capable of working to what is reasonably practicable and what is sensibly avoided. the trouble with these vague concepts is that they leave one open to being second-guessed by a politically (small p) oriented organisation which one day happens to have someone in place who wants to Make a Point one way or the other.
When you are in the dock on a Health & Safety charge following some incident(s), facing unlimited fines for your company/Department, prison sentence for you and your reputation in ruins, concentrating your mind on 'reasonably practicable' and your signature on the sign-off papers for third rail extension will not look so good.
The bothy electrification risk assessors on this forum will surely be standing well back.....
I visited Barcelona earlier in the year and was slightly surprised to see their Metro is OHLE. I'd assumed 3rd rail would be the natural method for a metro, but they seem to have gone for overhead, often rigid bar. Some of their lines date back to the 19th century, presumably they were lucky enough to have the space for that?
Though if they go for that in a metro application, third rail in wide open country seems hard to justify.
When you are in the dock on a Health & Safety charge following some incident(s), facing unlimited fines for your company/Department, prison sentence for you and your reputation in ruins, concentrating your mind on 'reasonably practicable' and your signature on the sign-off papers for third rail extension will not look so good.
The bothy electrification risk assessors on this forum will surely be standing well back.....
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