Great Western Main Line upgrade

[9] When the announcement was made in July 2009 to electrify the Great Western (along with the Liverpool-Manchester line), it represented the first big rail electrification project in the UK for 20 years.

[3] Prior to 2009, the only electrified portion of the Great Western was between London Paddington and Airport Junction (west of Hayes and Harlington).

This portion is equipped with a 25 kV AC overhead system which was implemented in 1997 in readiness for the Heathrow Express service commencing in early 1998.

However, in July 2009, the Department of Transport under the then Labour Government (in the run-up to the 2010 general election), announced that there would be a £1bn programme to electrify the whole of the Great Western from London to Swansea as well as to Bristol Temple Meads.

[19][20] The scheme announced by the government on 23 July 2009 stated that "work will begin immediately on the electrification of the Great Western Main Line between London, Reading, Oxford, Newbury, Bristol, Cardiff and Swansea, to be completed within eight years" (2016/2017).

[16] The proposed electrified route included:[16] Estimates showed that the Hitachi Super Express trains could reduce journey times from London Paddington to Swansea by 19 minutes.

[16] In an effort to minimise disruption during the electrification works, Network Rail developed new "factory engineering trains" to facilitate the process of installing overhead lines.

[23] After the 2010 UK general election in May 2010, the Conservative–Liberal Democrat coalition placed all major government capital expenditure, including the Great Western electrification scheme on hold pending a return-on-investment review.

Extension from Didcot to Swindon, Bath, Bristol and to South Wales would be dependent on a further assessment due in 2011 of the costs and implementation requirements of the IEP.

[25] On 1 March 2011, Hammond announced that rail electrification from Didcot Parkway to Bristol Temple Meads and Cardiff Central would go ahead.

HOPS will mix and lay 30 m3 (1,100 cu ft) of concrete per night, and all equipment and personnel will arrive at the site on board.

[34] The main part of the programme will go ahead as planned and should be delivered by March 2019, but the Cardiff to Swansea section will be delayed, to some time between 2019 and 2024.

[15] The Great Western Main Line was equipped with colour light signalling common to the rest of the United Kingdom.

At the time of the Ladbroke Grove rail crash (1999), the ATP (Automatic Train Protection) warning system was under trial.

[37] When the Department for Transport wrote the specification for the new trains for the IEP in November 2007, it was stated that the Great Western Main Line would be upgraded to ERTMS/ETCS level 2 in-cab signalling and trackside infrastructure.

[16] Signalling Solutions would resignal the 12 miles from Paddington to West Drayton, including the Airport branch, as part of the Crossrail project.

[5] Despite the initial limit of 125 mph, the increased acceleration and operational efficiency are expected to decrease the journey time from London to Bristol Temple Meads by 22 minutes.

Several stations along the Great Western are undergoing redevelopment or have recently been upgraded to cope with growing passenger numbers and to ease rail traffic congestion.

Bristol Temple Meads will be expanded into Digby Wyatt's 1870s extension to the original train shed,[54] built by Isambard Kingdom Brunel in 1840 as the terminus for the Great Western Main Line.

[55][56] To achieve rail access to the existing old platforms, the Bristol power box, opened in 1970 and controlling 114 route miles of track, will need to be decommissioned and demolished.

The new bridge is clad in ethylene tetrafluoroethylene (ETFE), the material which protects the Eden Project in Cornwall, despite which the roof initially gave problems with leaking.

[67] The development was criticised by Rail columnist Barry Doe for being at the wrong end of the station, having a leaking roof, a lack of seating and generally poor design.

[75] Severn Tunnel Junction serves as a Park and Ride station for commuters from southern Monmouthshire to Bristol, Newport and Cardiff and there is a local action group – the Severn Tunnel Action Group (STAG) – who are campaigning to enhance the Junction's status as a transport hub for the southern Monmouthshire area.

[16] On 12 July 2012, Transport Secretary Justine Greening announced that a new rail link connecting Slough and Heathrow had been given the go-ahead and would be operational by 2021.

In his March 2011 Budget, the Chancellor George Osborne approved a project to re-double this section of line, after several years of campaigning by local politicians.

[91] The Goring Gap Railway Action Group (formed in March 2015) complained that there had been insufficient consultation between Network Rail and residents of Goring-on-Thames about the visual impact of the overhead line supports.

Campaigners alleged that the removal amounted to a closure by stealth, with Network Rail apologising for not consulting residents or conforming to their code of best practice.

[99][100][101] There was subsequently a campaign for Pilning to receive the footbridge from Angel Road, following that station's closure in May 2019, but Network Rail stated that there was no financial justification for replacing the bridge.

[106] The RMT union called for assurances that the plans will not have an adverse impact on jobs at the UK's only train maker Bombardier.

[19] In February 2010, it was announced that the IEP (for long-distance express services) was suspended pending an independent report, with a decision on its viability to be given after the 2010 UK general election.