Editing Great Western Main Line (section)

{{short description|Principal main line railway in England}}
{{distinguish|West Coast Main Line|West of England line}}
{{Use British English|date=July 2015}}
{{Use dmy dates|date=June 2021}}
{{Infobox rail line
| box_width                       = 
| name                            = Great Western Main Line
| color                           = 
| image                           = Brunel's railway bridge at Maidenhead from the Thames Path National Trail, geograph 5893373 by Dave Kelly.jpg
| image_width                     = 
| caption                         = [[Maidenhead Railway Bridge]] carrying the line over the [[River Thames]].
| type                            = [[Commuter rail]], [[Higher-speed rail]]<ref>{{cite news |last1 = Bowen |first1 = Douglas John |title = Hitachi Rail Europe taps Huber+Suhner |url = http://www.railwayage.com/index.php/communications/hitachi-rail-europe-taps-huber-suhner.html |access-date = 2 December 2014 |work = Railway Age |date = 1 December 2014 |archive-date = 4 March 2016 |archive-url = https://web.archive.org/web/20160304212329/http://www.railwayage.com/index.php/communications/hitachi-rail-europe-taps-huber-suhner.html |url-status = dead}}</ref>
| system                          = [[National Rail]]
| status                          = Operational
| locale                          = {{ubl|[[Greater London]]|[[South East England]]|[[South West England]]}}
| start                           = [[Paddington station|London Paddington]]
| end                             = {{Stnlnk|Bristol Temple Meads}}
| stations                        = 25
| daily_ridership                 = 
| open                            = 30 June 1841 (complete line)
| owner                           = [[Network Rail]]
| operator                        = {{ubl|[[Great Western Railway (train operating company)|Great Western Railway]],|[[Elizabeth line]],|[[Heathrow Express]],|[[CrossCountry]]}}
| depot                           = {{ubl|[[North Pole depot|North Pole]],|[[Reading TMD|Reading]],|[[St Philip's Marsh depot|St Philip's Marsh]]}}
| stock                           = {{ubl|{{brc|158}}|{{brc|159}}|{{brc|165}}|{{brc|166}}|{{brc|220}}|{{brc|221}}|{{brc|345}}|{{brc|387}}|{{brc|800}}|{{brc|802}}}}
| linelength                      = {{convert|118|mi|19|ch|km|2|abbr=out}}
| tracks                          = Four (London to Didcot),<br />two (Didcot to Bristol)
| gauge                           = {{track gauge|uksg|lk=on}}
| old_gauge                       = {{track gauge|7ft0.25in|lk=on}}
| minradius                       = 
| electrification                 = [[25 kV AC|25 kV 50 hz AC]] [[Overhead line|OLE]] (London to Chippenham)
| speed                           = {{convert|125|mph|abbr=on|round=10}}
| signalling                      = [[Automatic Warning System|AWS]], [[Train Protection & Warning System|TPWS]], [[Automatic Train Protection (United Kingdom)|ATP]]
| map                             = [[File:Great Western Main Line map.png|321px]]
| map_state                       = uncollapsed
}}
{{Great Western Main Line diagram}}
The '''Great Western Main Line''' ('''GWML''') is a [[main line (railway)|main line]] [[railway]] in England that runs between [[Paddington railway station|London Paddington]] and {{stnlnk|Bristol Temple Meads}}. It connects to other main lines such as those from [[Reading to Taunton line|Reading to Penzance]] and [[South Wales Main Line|Swindon to Swansea]]. The GWML is presently a part of the national rail system managed by [[Network Rail]], while the majority of passenger services upon it are provided by the current [[Great Western Railway (train operating company)|Great Western Railway]] franchise.

The GWML was built by the original [[Great Western Railway]] company between 1838 and 1841, as a dual track line in the {{track gauge|84in|lk=on}} [[broad gauge]]. The broad gauge remained in use until 1892, after which standard gauge track has been exclusively used. Between 1877 and 1932, many sections of the GWML were widened to four tracks. During 1908, [[Automatic train control#United Kingdom|Automatic Train Control]] (ATC) was introduced as a safety measure. In 1948, the Great Western Railway, and thus the GWML, was merged into the [[Western Region of British Railways]].

During the 1970s, the GWML was upgraded to support higher line speeds, as a result of which many sections permitted {{cvt|125|mph|km/h}} operations, enabling the newly introduced [[InterCity 125]] high speed train (HST) to make faster journeys. [[British Rail]] proposed widespread electrification of the line in the late 1970s, although this was not speedily implemented. During the mid-1990s, a stretch of the GWML between London Paddington and [[Hayes & Harlington railway station|Hayes & Harlington]] was electrified using {{nowrap|[[25 kV AC]]}} overhead lines for the [[Heathrow Express]]. Further, although not total, electrification was carried out during the 2010s; this permitted the replacement of diesel-powered trains such as the InterCity 125 and {{brc|180}} with electric and [[Electro-diesel multiple unit|bi-mode train sets]] such as the [[Intercity Express Programme|Hitachi Super Express]] high speed trains, specifically the {{brc|800}} and {{brc|802}}. Due to budget overruns, the British government deferred electrification of the section through [[Bath Spa railway station|Bath Spa]] from [[Royal Wootton Bassett]] to [[Bristol]] in 2016.

The route includes dozens of [[listed building]]s and structures, including tunnel portals, bridges and viaducts, stations, and associated hotels. Presently, the GWML is electrified between London Paddington and Royal Wootton Bassett. In the long term, Network Rail plans to install [[European Rail Traffic Management System]] (ERTMS) in-cab signalling across the entire line.