Why was third rail mostly concentrated in the South?

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MotCO

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As the title states, why was third rail mostly restricted to South Eastern, Southern and South Western railways? Was it because other regions adopted diesel to replace steam? Was it down to the timing of the replacement of steam, i.e. did the early converters use diesel and later ones use electric, or vice versa?
 
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JonathanH

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As the title states, why was third rail mostly restricted to South Eastern, Southern and South Western railways? Was it because other regions adopted diesel to replace steam? Was it down to the timing of the replacement of steam, i.e. did the early converters use diesel and later ones use electric, or vice versa?

This will provide some explanation

https://en.wikipedia.org/wiki/London,_Brighton_and_South_Coast_Railway#Electrification
https://en.wikipedia.org/wiki/LSWR_suburban_lines#Electrification_of_the_LSWR_network
https://en.wikipedia.org/wiki/25_kV_AC_railway_electrification

Basically a point to do with timing - the Southern networks were first to electrify - they standardised on the approach introduced by the LSWR to have third rail. When it came to the routes north of the Thames, 1500V DC was initially in place which was replaced by 6.25kV AC and eventually 25kV AC.

https://en.wikipedia.org/wiki/Railway_electrification_in_Great_Britain
 
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mr_jrt

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As I understand it, it was mainly down to who was making the decisions at the time. One of the big benefits of electrification is greatly improved acceleration, so railways which had metro operations were always going to be driving adoption. The London Underground adopted the DC 3rd & 4th rail system it did due to Mr Yerkes's influence from his New York systems, and in time this filtered out over the interworked lines up to Watford, down to Wimbledon and out to Upminster. Seeing the benefits, the railways serving south London, being heavily metro focussed with little intercity traffic to speak of looked into it, and by this point OHLE AC electrification had been invented by Siemens in Germany, and was more efficient, so they started using that on their lines out of Victoria. The LSWR decided to go with third rail, maybe partially due to the interworking with the District line with it being a proven technology by then, and when they were grouped in the 20s, there was more third rail than OHLE, so the former LBSCR lines were converted to third rail. The third rail then spread outwards...
 

dgl

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History mainly I believe, the SR was one of the first companies to use main line electric traction and as such used the practices of the time, and installed quite a few route miles of 3rd rail, converting DC overhead systems when they were acquired so as to allow commonality, and a such as electrification increased with the Kent Coast and BML projects it was deemed sensible to continue with 3rd rail not least as overhead clearances would not be an issue saving the costly rebuilding of bridges and tunnels.

Now when routes such as the WCML were electrified that was much later and as such practices and technology had changed, this made high-voltage AC electrification possible which had great advantages over low voltage 3rd rail systems, primarily in transmission efficiencies and equipment costs, naturally this was selected for not only this but any future projects where an already installed 3rd rail system was either not present or insignificant, hence the use of 3rd rail for Bournemouth to Weymouth but the Paddington to Heathrow electrification, for instance, was 25kV.

As for diesel replacing steam, that originally, I believe, was a stopgap for electrification that never happened, plus for some lines electrification was not economically viable when compared to diesel, so unless full electrification of Britain's railways was the end goal some lines would never warrant electrification as long as Diesel is an option.
 

Saperstein

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There were a lot of different systems in operation in various parts of the country.

OHLE AC wasn’t just today’s 25KV back then but various systems had very different standards. 15KV on the Woodhead line for example.

Third rail survived in the former BR Southern region and was even extended on the Hastings lines in the mid to late 1980’s AFAIK.

In other parts of the country 25KV OHLE seemed to take over and is still being installed today, I’m not aware of any new Third rail systems.

Merseyrail of course is another exception and of course currently uses x-Southern region EMU’s.

I wonder if OHLE is favoured from a safety aspect or maybe cheaper as you don’t need as many sub-stations.

Saperstein.
 

johnmoly

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The Mersey Railway, the one under the river, adopted third rail electrification in 1903. The same year it was installed on the Liverpool to Southport line.
 

Peter Sarf

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As the title states, why was third rail mostly restricted to South Eastern, Southern and South Western railways? Was it because other regions adopted diesel to replace steam? Was it down to the timing of the replacement of steam, i.e. did the early converters use diesel and later ones use electric, or vice versa?

Early conversions from Steam used Direct Current electric both overhead (mainly 1.5kV) and DC third rail (mainly 750V). It was more suited to intensive suburban services so did not go far out of London or other cities (see below).

The overhead you see nowadays is Alternating Current 25kV. The technology for this did not exist as early as DC did and the UK was one of the last companies to adopt AC as standard in the 1960s.

The southern DC did not extend far out of London. The equivalent to the North of London was underground (not much goes very far South). So there was very roughly an even spread of DC third (& fourth rail) electrification in both North and South London suburbs.

Almost 100% of the Southern region (SE, S and SW) eventually got third rail. This was as Steam got replaced and the third rail got extended further and further until it reached the channel coast. It would have been AC but the London end of the lines was DC.

Some aberrations :-
1) South central had some DC overhead but that got changed to third rail long before nationalsation (1948).
2) Some southern freight yards had overhead (presumably 750V DC and used by class 71). This was to make life safer for staff. Electro-Diesels (class 73 & 74) obviated that need around the 1960s-70s.
3) Lines out of Liverpool Street were iirc originally 1.5kV DC but were converted to AC around the 1960s.

There was DC third rail outside London.
1) Liverpool had suburban lines that are DC third rail and this still survives. They Currently use class 507s and identical class 508s from Southwestern. These are about to be replaced.
2) Manchester had some with side contact. This is now a tram route.
3) Newcastle had suburban lines using DC third rail. These reverted to diesel in the late 60s/early 70s iirc. The units came to Southern.
4) Manchester to Sheffield and Wath had DC in the form of 1.5kV overhead. Most of the route got closed and the Manchester end was converted to 25kV AC.
 
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JonathanH

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Merseyrail of course is another exception and of course currently uses x-Southern region EMU’s.

Currently part of the fleet uses units which operated on the Southern as a stop-gap measure alongside ones built for Merseyside in the first place.
 

edwin_m

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There are useful documents on the development of electrification in the UK in the attached link (too many to quote): http://www.railwaysarchive.co.uk/do...hor=all&publisher=all&published=all&submit=Go

To summarise:
  • Early systems were suburban in nature and mostly used a voltage of around 600V dc (surviving ones later upgraded to 750V). On the main line this was by top contact third rail but the Underground used the same voltage via separate positive and negative rails. The two systems allowed inter-working, which was probably a major reason for the main line to adopt it.
  • There were some other systems. The LBSCR started electrifying with overhead line at 6.25kV low-frequency AC (not DC as suggested above). This was eliminated in the 1920s when the SR decided to standardise on the third rail system. Manchester-Bury was 1200V dc using a side-contact third rail.
  • In the 1920s the railways agreed to use 1500V DC for long-distance systems, as it appeared to be the best system available at the time. However progress was slow. The LNER was the most advanced, completing Manchester-Altrincham jointly with the LMS and initiating the Woodhead and Great Eastern suburban schemes completed by British Rail after WW2.
  • Other countries electrifying during this period mainly adopted 1500V or 3000V DC or 15kV low-frequency AC.
  • In the early 1950s France, despite having extensive 1500V electrification, adopted the new 25kV system for new schemes in areas not yet electrified. This used the standard industrial frequency of 50Hz with trains having transformers and rectifiers on board. Since then many other countries with DC systems have adopted 25kV for new schemes, and some have converted existing electrified routes.
  • Britain quickly decided to adopt the same system except for extensions in third rail areas, but with the voltage reduced to 6.25kV (still at 50Hz) on urban sections where providing electrical clearance for 25kV would be difficult. The GE scheme was converted to this system, as was Manchester-Altrincham as part of the 25kV electrification of the main line into Manchester. Despite using adjacent tracks at Manchester Piccadilly, Woodhead was left at 1500V until the main line closed in the 1980s and the residual Glossop/Hadfield service was converted.
  • Also in the 1980s it was established that the clearances for the full 25kV were much less than first thought, and the 6.25kV sections were upgraded to give 25kV throughout.
  • Some railway routes were converted to light rail from the 1980s onwards, with the Tyne and Wear Metro using 1500V (later extended over Network Rail to Sunderland), Docklands at 750V with a different (bottom contact) third rail and others at 750V overhead (including yet another voltage for Manchester-Altrincham).
  • Latest, as discussed on other threads, is that the safety authorities will not allow new top-contact third rail except in very specific circumstances. This makes it more difficult to consider electrifying the few remaining diesel "islands" on the Southern network. Dual voltage trains are now standard technology so it is fairly certain that any more significant extension of electrifiation from to the third rail network would use 25kV, but there are no plans to do this at present.
 

Yorkshire222

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One reason was that in those early times the electricity grid wasn't linked- towns had to have their own power stations (and naturally it was the larger towns that got them first). But even then the supply was unreliable. The only way for Southern to solve this was to build their own power station - this obviously required a big financial commitment but proved worthwhile in the long run.
 
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Sir Hebert Walker was the key player, GM of the LSWR from 1912 and the Southern until 1937. Although the LB&SCR system was technically far superior, based on German / Swiss practice, the LSWR had a greater mileage electrified at the grouping, and despite the need for more sub-stations, third-rail was far easier to install than all the OHLE paraphernalia. In the inter-war years this was a key benefit to effect quick improvements. I think the philosophy still applies today, and that the remaining diesel islands on the Southern should be converted - despite what the ORR might say. There is zero-chance of the third-rail being converted to 25kV AC, so what exactly is the risk of extending by a few miles?
 

randyrippley

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When you think about it, there were more third rail schemes in the north than in London, they just never got expanded due to war regional groudping and 1930s depression
Liverpool / Wirral underground
Liverpool-Southport
Liverpool Overhead
Manchester-Bury
Tyneside

If WW1 and the grouping hadn't happened then the L&Y would have electrified a lot more of the commuter lines around Manchester and possibly extended the Liverpool network, while the NER would have expanded the Tyne network
 

John Webb

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It's worth noting that the underground lines, especially the tube lines with cast-iron tunnel linings, used the separate positive and negative rails to minimise earth leakage currents from affecting the tunnel linings by avoiding the use of the running rails for heavy traction currents. Probably also made track-circuiting easier as well!
 

Mogz

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The Mersey Railway, the one under the river, adopted third rail electrification in 1903. The same year it was installed on the Liverpool to Southport line.

I think the Mersey Railway was originally fourth rail like London Underground and converted to third rail to be compatible with the ex-LMS Wirral Railway electrified lines in the mid 50s. If so, I’d be interested to know:

1. Why the Mersey Railway chose fourth rail in 1903 when third rail was already in use on the Liverpool Overhead Railway from the 1890s?

2. Why the LMS chose third rail for the Wirral electrifications of 1938 when the Mersey Railway was already using fourth rail?

Also,

3. I think I remember reading that the L&Y third rail electrification from Liverpool to Southport in the early 1900s actually used a fourth rail that was not in contact with the trains. How/why?
 
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