Current rails

[jamesb]

This might be a stupid question but:

I understand that the positive (third) current rail is located on right right hand side in the direction of travel in platforms, for safety reasons, so that it is further away from the platform edge. That makes sense.

But why does it then switch to the left outside stations? Wouldn't it have made more sense for it always to run on the right hand side, in the direction of travel?

More sense because:

- It would be less work and less connections having to transfer the current by cable from left to right on the approach to every station.

[Deleted]

Well then you would have two positive rails side by side in the six foot, which it strikes me would make crossing the track difficult.

[philthetube]

on most lines trains are reversed regularly, Jub and Vic excepted.

I was told it was to reduce the risk or arcs between the rails

[norbitonflyer]

Trains are not able to be reversed on the Bakerloo or District either. Picadilly trains could not be reversed until the Heathrow Loop was built, and 1973 stock was not designed to allow both-way-round coupling. Likewise, until trains ran all the way round the Hainault Loop, Central Line trains were not reversed, and 1962 stock was not designed to do so.

The side on which the positive conductor rail is placed depends on a number of factors, of which the position of platforms is but one. For example, at points and crossings, it is always on the side which is not interrupted.

[countryman]

Oct 18, 2016 21:20:38 GMT jamesb said:

This might be a stupid question but:

I understand that the positive (third) current rail is located on right right hand side in the direction of travel in platforms, for safety reasons, so that it is further away from the platform edge. That makes sense.

But why does it then switch to the left outside stations? Wouldn't it have made more sense for it always to run on the right hand side, in the direction of travel?

More sense because:

- It would be less work and less connections having to transfer the current by cable from left to right on the approach to every station.

My understanding is that the rail is, if possible on the side away from the platform edge. When the platforms are in the island configuration this will mean that they will be on the left. Of course, at places with a centre platform, like White City, the  rails will have to be close to one platform edge.

[stapler]

Which side in fact are they on at Stratford P3) (Loughton and White City?

[Chris M]

I believe they are on the right hand side in the direction of travel at Stratford, as this is the side away from the original platform. This platform is also narrower and busier so the more likely for someone to fall from, meaning that it is probably safest (as well as cheapest) to leave it where it is.

At Loughton the conductor rail is on the platform 3 (eastbound island) side, which is on the left for an eastbound train. The way this platform is currently used for reversing trains means that platform 3 is used almost exclusively for alighting.

At White City the rail is adjacent to platform 2 (westbound island), on the right for a westbound train. I'm much less familiar with how White City operates, but if it is used like Loughton then again this will primarily be the side used by alighting passengers.

At Arnos Grove, which similarly has a central track with platforms either side, I have a photograph that suggests the current rail is on the platform 2 side (north/eastbound island) and on the left for a north/eastbound train. If this platform is also mainly used for reversing trains, then the current rail will be on the alighting side also.

Taken together these suggest that having the rail adjacent to the alighting platform is seen as preferable.

At Morden, there are two tracks with platforms either side (1 and 2, 3 and 4). On the latter track, the conductor rail seems to be on the platform 4 side (I have two photos showing it isn't on the platform 3 side), which is on the right for an arriving train. I have no photos showing the position of the conductor rail on the other track.

At Cockfosters and Uxbridge there are also tracks with platforms on both sides, however I don't have any photos to that show which side the rail is on.

[countryman]

Oct 18, 2016 21:32:23 GMT @benp said:

It's to help the collector shoes wear out more or less evenely as opposed to one side constantly under wear. Same reason the contact wire for overhead lines isnt always in the centre staggers left to to even put the wear

If the rails were on the same side (say the left) running in both directions, the wear would even out. This also applies if there is a loop. A train leaving Cockfosters and running round Heathrow loop will wear shoes in a certain pattern the first time. When it runs round again the same pattern will wear the opposite side to compensate. If the train runs to Rayner's Lane or Ruislip in between the wear will even out. 

[countryman]

The issue here is not necessarily whether the train is arriving or departing, but the danger of falling on the live rail when the platform is unoccupied by a train.

[Chris M]

Oct 19, 2016 15:44:27 GMT countryman said:

The issue here is not necessarily whether the train is arriving or departing, but the danger of falling on the live rail when the platform is unoccupied by a train.

That makes sense - people are less likely to be hanging around on an arrival platform than a departure platform.

[stapler]

Many thanks, Chris M

[Deleted]

Oct 19, 2016 13:02:01 GMT Chris M said:

I believe they are on the right hand side in the direction of travel at Stratford, as this is the side away from the original platform. This platform is also narrower and busier so the more likely for someone to fall from, meaning that it is probably safest (as well as cheapest) to leave it where it is.

At Loughton the conductor rail is on the platform 3 (eastbound island) side, which is on the left for an eastbound train. The way this platform is currently used for reversing trains means that platform 3 is used almost exclusively for alighting.

At White City the rail is adjacent to platform 2 (westbound island), on the right for a westbound train. I'm much less familiar with how White City operates, but if it is used like Loughton then again this will primarily be the side used by alighting passengers.

At Arnos Grove, which similarly has a central track with platforms either side, I have a photograph that suggests the current rail is on the platform 2 side (north/eastbound island) and on the left for a north/eastbound train. If this platform is also mainly used for reversing trains, then the current rail will be on the alighting side also.

Taken together these suggest that having the rail adjacent to the alighting platform is seen as preferable.

At Morden, there are two tracks with platforms either side (1 and 2, 3 and 4). On the latter track, the conductor rail seems to be on the platform 4 side (I have two photos showing it isn't on the platform 3 side), which is on the right for an arriving train. I have no photos showing the position of the conductor rail on the other track.

At Cockfosters and Uxbridge there are also tracks with platforms on both sides, however I don't have any photos to that show which side the rail is on.

They're on the left at Stratford westbound, but I think that's what you meant to say, because the original platform (3) is on the right and the positive rail is on the same side as the new platform (3a).

The positive rail is on the platform 1 side at Morden (left hand side for trains arriving from South Wimbledon), which makes sense as platform 1 is (almost?) never used.

At Cockfosters the positive rail is also on the left hand side for arriving trains - alongside platform 2.

At Uxbridge it's on the right hand side for arriving trains - alongside platform 3.

[Chris M]

Oct 19, 2016 22:34:03 GMT tut said:

They're on the left at Stratford westbound, but I think that's what you meant to say, because the original platform (3) is on the right and the positive rail is on the same side as the new platform (3a).

Whoops, yes indeed. A simple case of my getting my east and westbound mixed up (probably as it's been a very long time since I've caught a westbound Central line train from Stratford but get an eastbound at least once a month, so am more used to trains arriving from that direction!)

[John Tuthill]

Oct 19, 2016 15:44:27 GMT countryman said:

The issue here is not necessarily whether the train is arriving or departing, but the danger of falling on the live rail when the platform is unoccupied by a train.

I wonder when the LTE came up with this philosophy? In 'London's Disused Underground Stations' by J.E. Connor, it shows pictures of the original 'Osterley' station with the live rails nearest to the platforms, a similar situation at Belmont Road, and at 'Lords'

[class411]

Oct 20, 2016 10:43:21 GMT John Tuthill said:

Oct 19, 2016 15:44:27 GMT countryman said:

The issue here is not necessarily whether the train is arriving or departing, but the danger of falling on the live rail when the platform is unoccupied by a train.

I wonder when the LTE came up with this philosophy? In 'London's Disused Underground Stations' by J.E. Connor, it shows pictures of the original 'Osterley' station with the live rails nearest to the platforms, a similar situation at Belmont Road, and at 'Lords'

Probably about five minutes after the first time someone fell on a platform side live rail.

[Harsig]

Oct 20, 2016 12:47:29 GMT class411 said:

Oct 20, 2016 10:43:21 GMT John Tuthill said:

I wonder when the LTE came up with this philosophy? In 'London's Disused Underground Stations' by J.E. Connor, it shows pictures of the original 'Osterley' station with the live rails nearest to the platforms, a similar situation at Belmont Road, and at 'Lords'

Probably about five minutes after the first time someone fell on a platform side live rail.

According to Alan Jackson's 'London's Metropolitan Railway' the change was not made because of the risks to people falling onto the conductor rail from the platform, but because of the operating problems caused by other objects being dropped from platform. To quote:

Another early change was in the position of the positive conductor rails at stations, which were moved to the six-foot way from 1909 onwards and provided with double guard rails, the work being done gradually as ordinary maintenance. This change was not made for humanitarian reasons; much to the chagrin of the operating department, metal objects had fallen from the platforms to form a short circuit between the conductor rail and the continuous running rails.

Such a short circuit would be a positive earth, and even today these still have the potential to cause the underground problems such as signal failures. Presumably the sort of metal objects being referred might include things like umbrellas.

[class411]

Oct 20, 2016 13:52:46 GMT Harsig said:

Oct 20, 2016 12:47:29 GMT class411 said:

Probably about five minutes after the first time someone fell on a platform side live rail.

According to Alan Jackson's 'London's Metropolitan Railway' the change was not made because of the risks to people falling onto the conductor rail from the platform, but because of the operating problems caused by other objects being dropped from platform.

Almost impossible to believe, today, with the never ending ascension of the Safety Elf, that there was a time when danger to human life could be ignored in such a cavalier manner.

How very fortunate for the passengers of the time that there were pecuniary disadvantages that aligned with their own interests in continued mortal existence.

[brigham]

I'm sure that, had passengers falling onto the live rail been a common occurrence, then the live rail would have been moved. As it is, the common occurrence must have involved objects dropped from the platform.
Does anybody have the figures? Do people fall from platforms on a regular basis? Have they always done so?

[Chris M]

The Telegraph had an article about this in January.
"In 2003, TfL said, 56 PTI falls [people falling at the platform-train interface] were recorded. In 2014, it was 298, which is an increase of 432%."
" In 2002/3 a total of 942 million passenger journeys were made. The 56 PTI falls in that year made up 0.00005% of all journeys, or 1 in 17 million journeys.
In 2013/14, there were 1.26 billion passenger journeys on the Tube and 298 PTI falls. These 298 falls made up 0.00236% of all journeys that year, or 1 in 4.2 million journeys. "

[superteacher]

Oct 19, 2016 6:56:03 GMT norbitonflyer said:

Trains are not able to be reversed on the Bakerloo or District either. Picadilly trains could not be reversed until the Heathrow Loop was built, and 1973 stock was not designed to allow both-way-round coupling. Likewise, until trains ran all the way round the Hainault Loop, Central Line trains were not reversed, and 1962 stock was not designed to do so.

The side on which the positive conductor rail is placed depends on a number of factors, of which the position of platforms is but one. For example, at points and crossings, it is always on the side which is not interrupted.

Trains can be reversed on the District by being sent to High Street Ken from Gloucester Road, then onto Earls Court. Doesn't happen very often, but certainly has in the past.

[revupminster]

Just another thought the signal current (5-10vac) would enter the right hand running rail to the signal relay and return to the left hand running rail back to the supply. Early engineers thought it best to keep the 630 dc traction current supply as far away as possible wherever possible.

[castlebar]

@ norbiton

actually, Picc trains could be reversed before the Heathrow Loop

Once in the 60s or early 70s, the Picc lent some stock to the Northern which came back "wrong way around". It was reversed via using the Earls Court/Kensington triangle, and photos of this do exist taken at Earls Court & High St Ken I think

[Deleted]

Oct 20, 2016 21:23:28 GMT revupminster said:

Just another thought the signal current (5-10vac) would enter the right hand running rail to the signal relay and return to the left hand running rail back to the supply. Early engineers thought it best to keep the 630 dc traction current supply as far away as possible wherever possible.

It can be anything from 5-30v and open circuit voltage can be upto 100v.

[class411]

Oct 21, 2016 8:04:30 GMT castlebar said:

@ norbiton

actually, Picc trains could be reversed before the Heathrow Loop

Once in the 60s or early 70s, the Picc lent some stock to the Northern which came back "wrong way around". It was reversed via using the Earls Court/Kensington triangle, and photos of this do exist taken at Earls Court & High St Ken I think

That is interesting.

In particular, I wonder why Picc trains need(ed) (or are/were preferred to be) a particular 'way round'.

[edb]

Oct 20, 2016 17:44:21 GMT Chris M said:

The Telegraph had an article about this in January.
"In 2003, TfL said, 56 PTI falls [people falling at the platform-train interface] were recorded. In 2014, it was 298, which is an increase of 432%."
" In 2002/3 a total of 942 million passenger journeys were made. The 56 PTI falls in that year made up 0.00005% of all journeys, or 1 in 17 million journeys.
In 2013/14, there were 1.26 billion passenger journeys on the Tube and 298 PTI falls. These 298 falls made up 0.00236% of all journeys that year, or 1 in 4.2 million journeys. "

Do you think this increase is likely due to the increased value of personal items such as mobiles and ipods?

[norbitonflyer]

Oct 21, 2016 8:04:30 GMT castlebar said:

@ norbiton

actually, Picc trains could be reversed before the Heathrow Loop

It was reversed via using the Earls Court/Kensington triangle, and photos of this do exist taken at Earls Court & High St Ken I think

But to reverse them they had to go off the Piccadilly Line, and were presumably not in service. D78 stock has indeed been round the third side of the triangle as an extempore measure (and, I believe, in service), but it has always been sent back again as soon as possible. Looking at Carto Metro, it seems that trains to and from Gloucester Road cannot use the bay platforms at High Street Ken, so presumably any reversal has to be done in the through platforms (specifically platform 2, using the trailing crossover to return to Earls Court or Gloucester Road) I don't know whether platform 2 is long enough to take a D78 (or 1973 stock) in service, nor whether the aforementioned trailing crossover is authorised for trains in passenger service.

Some early underground stock, notably on the City& South London and the Great Northern & City had asymmetric current collection arrangements, meaning that the trains could not have operated had they been turned round. However, as both lines were isolated shuttles, there was zero probability of this happening.

(On the C&SLR, the live rail was between the rails but off-centre to allow room for the coupling gear. The GN&CR had both the positive and negative rails outside the running rails, one each side).

[Deleted]

Platform 2 at HSK can take a D stock

[Chris M]

Oct 21, 2016 9:56:54 GMT edb said:

Oct 20, 2016 17:44:21 GMT Chris M said:

The Telegraph had an article about this in January.
"In 2003, TfL said, 56 PTI falls [people falling at the platform-train interface] were recorded. In 2014, it was 298, which is an increase of 432%."
" In 2002/3 a total of 942 million passenger journeys were made. The 56 PTI falls in that year made up 0.00005% of all journeys, or 1 in 17 million journeys.
In 2013/14, there were 1.26 billion passenger journeys on the Tube and 298 PTI falls. These 298 falls made up 0.00236% of all journeys that year, or 1 in 4.2 million journeys. "

Do you think this increase is likely due to the increased value of personal items such as mobiles and ipods?

Possibly a part of it but far more significant I think will be the increase in crowding on platforms and a decrease in general awareness of people to their surroundings (and this is largely due to electronic devices).

[norbitonflyer]

Oct 21, 2016 9:54:21 GMT class411 said:

I wonder why Picc trains need(ed) (or are/were preferred to be) a particular 'way round'.

Most Underground stock is "handed". In order to avoid duplication of electrical, air, etc connections, most Underground stock is "handed". Compare these two "standard stock" cars




noting in particular the positions of the three boxes covering sockets low on the cab front.

Tubeprune explains the problem in detail

Thus the two ends of each car (in car stock - up to Q and "standard") or unit (R and 1938 onwards) are different, (known as A and D) and each end can only be coupled to the opposite type of another car, which must therefore be the same way round. (Anyone who is familiar with a Brio train sets, with their magnetic couplings, will be familiar with the problem!)

To ensure any car/unit can couple to any other it is necessary to keep them all facing the same way. This is not difficult on end-to-end shuttles like the Bakerloo or Victoria (or the Piccadilly until 1986), but if a unit does get reversed it will be unable to couple to any other. Note that Piccadilly trains are made up of two units, which occasionally swap partners. Each train has to include one unit of each type*. If one train gets reversed, it will be incompatible with the rest of the fleet.

( *There are some double ended 1973 stock units, one end of which can couple to an "A" unit and the other to a "D" unit - although not, at least in practice, at the same time!)

Some lines with terminal loops , such as the Central when White City was the terminus, and the Hampstead Tube (Embankment, and later Kennington) had to cope with the problem of trains being opposite ways round on a routine basis, but at least in this case there were likely to be roughly equal numbers of units / cars facing each way so a match would not be difficult to find - albeit trains would be constantly switching from one subfleet to another every time they went round the loop. In the days of "car" stock both lines had turntables to alleviate this problem, but turning an entire unit is a rather different proposition. It was presumably because of the Kennington Loop that some of the trains loaned by the Piccadilly to the Northern were returned facing back to front.

Until the arrival of 1992 stock trains did not run all the way round the Hainault Loop. Care was taken that the few trains which ran from Central London to Hainault via Woodford (or to Woodford via Hainault) were returned back the way they had come, even if they had spent the night in Hainault depot facing the "wrong way".

More recently, stock has been built which can couple either way round - examples include 1972 stock, 1992 stock, A stock and C stock,. Note that the lines on which they were/are used all have loops or triangles (Kennington, Hainault, Watford, and Aldgate/Kensington respectively - the latter being used to turn trains from time to time to even out wheel wear). But D stock, 1967, 1973 and 1983 stock were built for lines without terminal loops, and were "handed" (In 1973, London's future airport expansion was expected to be at Maplin, not a fourth terminal at Heathrow!) 2009 and S stock are, I believe, indivisble seven or eight car units and so are not expected to swap partners routinely, so it doesn't mater which way round they are.

[John Tuthill]

Oct 21, 2016 13:25:10 GMT norbitonflyer said:

Oct 21, 2016 9:54:21 GMT class411 said:

I wonder why Picc trains need(ed) (or are/were preferred to be) a particular 'way round'.

Most Underground stock is "handed". In order to avoid duplication of electrical, air, etc connections, most Underground stock is "handed". Compare these two "standard stock" cars




noting in particular the positions of the three boxes covering sockets low on the cab front.

Tubeprune explains the problem in detail

Thus the two ends of each car (in car stock - up to Q and "standard") or unit (R and 1938 onwards) are different, (known as A and D) and each end can only be coupled to the opposite type of another car, which must therefore be the same way round. (Anyone who is familiar with a Brio train sets, with their magnetic couplings, will be familiar with the problem!)

To ensure any car/unit can couple to any other it is necessary to keep them all facing the same way. This is not difficult on end-to-end shuttles like the Bakerloo or Victoria (or the Piccadilly until 1986), but if a unit does get reversed it will be unable to couple to any other. Note that Piccadilly trains are made up of two units, which occasionally swap partners. Each train has to include one unit of each type*. If one train gets reversed, it will be incompatible with the rest of the fleet.

( *There are some double ended 1973 stock units, one end of which can couple to an "A" unit and the other to a "D" unit - although not, at least in practice, at the same time!)

Some lines with terminal loops , such as the Central when White City was the terminus, and the Hampstead Tube (Embankment, and later Kennington) had to cope with the problem of trains being opposite ways round on a routine basis, but at least in this case there were likely to be roughly equal numbers of units / cars facing each way so a match would not be difficult to find - albeit trains would be constantly switching from one subfleet to another every time they went round the loop. In the days of "car" stock both lines had turntables to alleviate this problem, but turning an entire unit is a rather different proposition. It was presumably because of the Kennington Loop that some of the trains loaned by the Piccadilly to the Northern were returned facing back to front.

Until the arrival of 1992 stock trains did not run all the way round the Hainault Loop. Care was taken that the few trains which ran from Central London to Hainault via Woodford (or to Woodford via Hainault) were returned back the way they had come, even if they had spent the night in Hainault depot facing the "wrong way".

More recently, stock has been built which can couple either way round - examples include 1972 stock, 1992 stock, A stock and C stock,. Note that the lines on which they were/are used all have loops or triangles (Kennington, Hainault, Watford, and Aldgate/Kensington respectively - the latter being used to turn trains from time to time to even out wheel wear). But D stock, 1967, 1973 and 1983 stock were built for lines without terminal loops, and were "handed" (In 1973, London's future airport expansion was expected to be at Maplin, not a fourth terminal at Heathrow!) 2009 and S stock are, I believe, indivisble seven or eight car units and so are not expected to swap partners routinely, so it doesn't mater which way round they are

And when this scenario was reversed so to speak, the Piccadilly reversed the units by means of the Earls Court/HSK/Gloucester Rd triangle.