British Rail Class 317

The British Rail Class 317 alternating current electric multiple units (EMUs) were built by BREL York in two batches, from 1981–82 and 1985-87. They were the first of several classes of British Rail EMU to be based on the all-steel Mark 3 bodyshell, departing from the "PEP"-aluminium design which had spawned the earlier Class 313 to Class 315. The Mark 3 bodyshell was also the basis of Class 318, Class 455, and the diesel Class 150.

Class 317/1
The first batch of 48 units, built in 1981-82, were classified as Class 317/1. Units were numbered in the range 317301-348, and had a maximum speed of 100 mph. Each unit consisted of four carriages; two outer driving 2nd class only vehicles, an intermediate trailer with both 1st and 2nd class, and a motor vehicle with 2nd class seating, roof mounted Stone Faiveley AMBR pantograph and four GEC G315BZ traction motors. The technical description of the formation of the units is DTSO(A)+MSO+TCO+DTSO(B). Individual carriages were numbered as follows:
 * 77000-77047 - DTSO(A)
 * 62661-62708 - MSO
 * 71577-71624 - TCO
 * 77048-77095 - DTSO(B)

These units were built to operate services on the newly electrified London St. Pancras to Bedford route. They replaced the elderly and unreliable Class 127 diesel multiple units. However, they did not enter service immediately due to an industrial dispute with the unions over Driver only operation, and the diesel units lingered on until finally being replaced in mid-1983. Units were delivered in the standard livery of BR blue/grey.

In 1986, the route came under control of the Thameslink subsector of newly created Network SouthEast. From 1987, new dual-voltage Class 319 units were introduced on the route, allowing the creation of a new cross-London service, from Bedford to Brighton, via Farringdon and City Thameslink station. The Class 317 units were displaced to outer-suburban services on the WCML out of London Euston station, to Milton Keynes and Northampton. They replaced the slam-door Class 310 units, which subsequently transferred to the London, Tilbury and Southend railway.

However, the use of Class 317 units out of Euston again proved to be short-lived. In 1989, the second batch of new Class 321 were introduced onto WCML services. The Class 317 units were again displaced, this time to the Great Northern and West Anglia routes out of London King's Cross and London Liverpool Street, where they joined the second batch units. Therefore, for the first time, the entire Class 317 fleet was operating in the same place.

Class 317/2
The second batch of 20 units, built in 1985-86, were classified as Class 317/2. Units were numbered in the range 317349-368. In 1987, a further four units were built, numbered 317369-372. Each unit consisted of four carriages; two outer driving 2nd class only vehicles, an intermediate trailer with both 1st and 2nd class, and a motor vehicle with 2nd class seating, roof mounted Stone Faiveley AMBR pantograph and four GEC G315BZ traction motors. Thus, each unit was formed DTSO(A)+MSO+TCO+DTSO(B). Individual carriages were numbered as follows:
 * 77200-77219 and 77280-77283 - DTSO(A)
 * 62846-62865 and 62886-62889 - MSO
 * 71734-71753 and 71762-71765 - TCO
 * 77220-77239 and 77284-77287 - DTSO(B)

The second batch units were built to operate outer-suburban trains on the Great Northern route from London King's Cross to Stevenage, Cambridge and Peterborough. Like the first batch units, they were delivered in BR Blue/Grey livery. The units replaced the slam-door Class 312 units, dating from 1975, which subsequently transferred to the Great Eastern Main Line and London-Tilbury-Southend routes. Like the DC class 455 units, several aspects of the exterior were modified, with metal hopper ventilators replaced with larger panes of glass and the 'headcode indicator' flat front replaced with a rounded design.

In 1986, the route came under the control of the newly created Network SouthEast, which introduced a bold new blue, red and white livery. The extension of the overhead line equipment soon allowed the units to work services on the West Anglia route from London Liverpool Street to Cambridge. In 1992, electrification spread north from Cambridge to Ely and King's Lynn, allowing the replacement of locomotive-hauled trains.

The closely related Class 318 units which were built for the Ayrshire Coast electrification in Scotland, are effectively a 3-car version of the same design, but with a lower speed capability of 90 mph and are fitted with Brush traction motors in place of GEC traction motors.

Former operations
With the privatisation of Britain's railways, the Class 317 fleet was incorporated into the West Anglia Great Northern (WAGN) franchise. Since then, various changes have occurred to the fleet, as units have been swapped and franchises have changed. The following companies operated Class 317s after privatisation but are no longer involved or no longer exist.

West Anglia Great Northern Railway (WAGN) & First Capital Connect (FCC)
WAGN used the Class 317 fleet on various services, including all London Liverpool Street to Cambridge services on the West Anglia route, and many stopping services to intermediate destinations. The fleet also worked services on the Great Northern route, from London King's Cross to Cambridge, Peterborough, Hertford, Stevenage and King's Lynn, plus at weekends when the line to Moorgate was closed, the units operated inner suburban services from London King's Cross to Letchworth Garden City, Hertford and Welwyn Garden City.

In 1998/99, WAGN started to refurbish its Class 317/2 fleet. The work was carried out by Railcare (now owned by Alstom) at Wolverton Works, and involved the fitting of Chapman bespoke high back seats in the 2+2 layout, and a small area to the 3+2 layout in the PTSO under the pantograph. The TCO vehicle became TSO as first class was moved to a cabin aboard a DTSO vehicle, which is now known as a DTCO vehicle. The units were outshopped in a new livery of white, with a grey band across the window area, blue and yellow bands on the lower half of the body, red doors, and a grey sweep at the cab ends. The Stone Faiveley AMBR pantograph was replaced by the industry standard Brecknell Willis High Speed design. Units were reclassified as Class 317/6 and were renumbered into the range 317649-672.

Many of the WAGN Class 317/1 units still wore the Network SouthEast (NSE) blue and red livery dating from 1986. In 2001, a new livery of metallic purple with lilac doors was introduced. The first unit so treated was 317 312, which had recently returned from loan to LTS Rail. The livery was progressively applied to the Class 317/1 fleet, with the final NSE examples (317 328 & 317 345) disappearing by mid-2004. By April 2004, the only units not repainted were 317301-307, which were hired to Thameslink and remained in LTS livery. The livery has also been applied to Class 313 and Class 315 units.

In April 2004, the WAGN franchise was split into the Great Northern and West Anglia routes. The latter became part of the new National Express East Anglia franchise, which operated under the title of One Railway. The Great Northern was temporarily operated independently under the WAGN brand name, until it was merged with the Thameslink franchise in April 2006. These changes resulted in the Class 317 fleet being divided among First Capital Connect and National Express East Anglia.

LTS Rail & c2c
In 1996, LTS Rail began to hire Class 317/1 units from its sister Prism Rail franchise WAGN for use on the London, Tilbury and Southend railway. At first only two units were hired, but by mid-1997 this had increased to a total of 18 units. Units were maintained at LTS Rail's main East Ham Depot.

The Class 317 units enabled LTS Rail to replace the elderly Class 302 slam-door EMUs, the last examples of which were withdrawn in 1998. The Class 317 units also replaced some of the Class 310 fleet on off-peak workings, pending introduction of new Class 357 "Electrostar" units.

Many of the units hired to LTS Rail were repainted in a variation of the existing Network SouthEast blue, red and white livery. The red stripe was replaced with a green stripe, and both the blue band and green stripe extended to the cab ends.

The units were slowly returned to WAGN from 1999, with the introduction of the new "Electrostar" units. The last examples were returned by 2000. However, unreliability of the "Electrostars" meant that four units were still hired on a daily basis until 2002. These units were maintained as part of the main WAGN fleet, and therefore the specific units involved changed when units required maintenance at WAGN's Hornsey TMD depot.

Thameslink
In 2002, Thameslink began hiring four Class 317/1 units from WAGN to allow it to run additional Bedford to Moorgate services. Unlike when units were hired to LTS Rail, specific units were not involved. Instead, units were still maintained by WAGN and only hired for a fortnight. Two units each week were transferred in each direction, generally being hauled over the non-electrified route by two Class 31 locomotives provided by Fragonset Railways or Class 47 locomotives with barrier vehicles at either end of the Class 317.

In 2004, when the WAGN franchise was split, twelve Class 317/1 units were transferred to Thameslink from the Great Northern route. This was because a planned route blockade for engineering works meant that extra units were required for Bedford services. The Class 317 units were replaced on Great Northern by Class 365 "Networkers", themselves displaced from South Eastern Trains by new Class 375 "Electrostars".

The Class 317 units transferred to Thameslink were maintained at the newly built Bedford Cauldwell depot in Bedford. They were restricted to services on the Northern half of the franchise only, as only dual-voltage or DC units can operate South of Farringdon. All of the units were returned to National Express East Anglia following the end of the blockade.

National Express East Anglia
On 1 April 2004, the West Anglia and Stansted Express routes became part of the new One franchise.

This was operated under the brand name 'one' until 26 February 2008, when it was rebranded as National Express East Anglia. Currently, the units have one of six different liveries: the old WAGN white; a debranded version of 'one' livery (minus the rainbow car ends); the same but with a white, National Express branded, stripe; two different Stansted Express liveries and the new National Express corporate scheme, similar to that of National Express East Coast and National Express Coaches.

National Express East Anglia secured the bid for thirty brand new Bombardier Class 379 trains which had all entered service as of August 2011.

Stansted Express
In 2000, nine Class 317/1 units were selected to be refurbished for the dedicated Stansted Express service, from London Liverpool Street to Stansted Airport, replacing the previously dedicated Class 322 units. The work was again carried out by Railcare at Wolverton, and included the fitting of luggage racks. The units also received a revised front end design, and a new metallic blue livery. The nine units were reclassified as Class 317/7, and were renumbered such that the last two digits of the set number remained unchanged. Again some Class 317/7 units have had their original Stone Faiveley AMBR pantograph replaced by the Brecknell Willis High Speed design.

In 2006 twelve further units were refurbished by Wabtec Doncaster, to a slightly different design. These units were reclassified as Class 317/8, and given a light blue (distinct from that used on the rest of the 'one' fleet) livery.

Both Classes 317/7 and 317/8 could occasionally be found working on West Anglia services and also it was not uncommon for Classes 317/5 and 317/6 units to work Stansted Express services alongside the dedicated Classes 317/7 and 317/8.

Following the arrivals of the new Class 379 units on Stansted Express services, the Class 317/7s and 317/8s were originally used alongside other Class 317s as a common pool. This changed when Abellio took over the East Anglia franchise on 5 February 2012, as the Class 317/7s were deemed too expensive to lease and surplus to requirements, and so they entered storage. Two have since returned to use with Greater Anglia, with the demonstrator unit to follow.

West Anglia
The West Anglia route is operated using the 24 strong Class 317/6 fleet, supplemented with 15 standard Class 317/1 units. They are mainly used on services from London Liverpool Street to Bishop's Stortford, Hertford East and Cambridge. The fifteen Class 317/1 units have been refurbished and renumbered into the 3175xx series.

Current operations
, all Class 317s are operated by Govia Thameslink Railway (Great Northern), Abellio Greater Anglia or London Overground.

Govia Thameslink Railway
Govia Thameslink Railway currently operates the 12 strong Class 317/1 fleet from when the new franchise began on 14 September 2014. These units operate Great Northern services.

Abellio Greater Anglia
The Abellio Greater Anglia franchise is operated using 15 Class 317/5 units, 24 Class 317/6 units and 6 Class 317/8 units. They are mainly used on medium-distance services between London Liverpool Street / Stratford and Broxbourne / Hertford East and on longer distance services between Liverpool Street / Stratford and Bishop's Stortford, Harlow Town and Cambridge. They are also used on some Bishops Stortford/Stansted Airport - Cambridge services. In addition to this, the newly refurbished demonstrator unit 317722 also sees uses with AGA.

London Overground
On 31 May 2015, London Overground took over operation of the Lea Valley Lines using 8 units Class 317/7 (317708 - 317710, 317714, 317719, 317723, 317729, 317732) and 6 units Class 317/8 (317887-317892).

Fitting of new traction equipment
Bombardier Transportation is currently using off-lease Class 317/7 unit 317722 as a test-bed unit. It is being rebuilt as a pre-series unit with new traction equipment. The unit will have its original DC motors and thyristors removed and four new AC motors and two 3-phase converters fitted. The original transformer will remain in place. Bombardier say that AC motors are more reliable than DC ones and require significantly less maintenance. The bogies must be modified for the new motors. This will also bring significant cost savings as the bogies don't need to be replaced. Regenerative braking will also be fitted. A new interior will be fitted to the driving trailer standard open 77021 and motor standard open 62682. This work will extend the life of the Class 317 by 20 years. Bombardier will evaluate the performance of the unit compared to a conventional Class 317.

The re-traction work will take place at the same time as a £1 million interior refurbishment of two vehicles of the same unit. The interiors will be refurbished in a Metro style layout and provide a direct contrast to the 3+2 and 2+2 seating currently in use. Trials, to test the reaction of passengers, will commence with Greater Anglia in mid-2014. If the new interior gets a positive reaction the full Class 317 fleet could be refurbished by the end of 2017.

Replacement
Govia Thameslink Railway have announced that they will be replacing all Class 317 and Class 321 on Great Northern services in 2016 after the transfer of Class 377 "Electrostar" from the Thameslink route.

London Overground will also replace the Class 317s it uses in 2018. In July 2015 TfL announced that it would place a £260m order for 45 Bombardier Aventra EMUs, similar to those that will be used by Crossrail, to be introduced on the West Anglia Routes, taken over from Abellio Greater Anglia on 31 May 2015, in 2018.