The works were part of Network Rail's £60 million Railway Upgrade Plan in order to prepare the Great Western Main Line for electrification from 2018.
The improvement programme took place over Christmas and the New Year, totalling 325,000 hours of work.
The works were undertaken in partnership with Great Western Railway (GWR).
Upgrades included:
• Major track and signalling upgrades at locations in Berkshire and west London including Maidenhead, Acton, Old Oak Common and Stockley.
• Station upgrades at Ealing Broadway, West Ealing, Hayes & Harlington, Southall and Maidenhead
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• Upgrading the overhead power lines between Acton and the junction to Heathrow airport
• Re-aligning the tracks at Heathrow junction and installing a new set of points.
• Electrification preparation work in west London and Berkshire
• The extension of platform 14 at Paddington station
• The replacement of Stratton Green bridge in Swindon with a new, higher bridge to make the additional room needed for the overhead electrification lines that will be installed underneath
In addition, 1,527 metres of new track was installed along with 6,300 concrete sleepers, 57,800 tons of ballast, over 11,700 metres of new overhead electrification wiring and 174 miles of new signal cables.
Network Rail's MD for the Western route, Mark Langman, said: "Our work over this Christmas and New Year was one of the biggest packages of improvement work on the Western route to date.
"Now these projects are complete, they will pave the way for the new fleet of longer, faster, quieter and greener electric trains, and for the introduction of Crossrail services from 2018 that will provide passengers travelling from the south east with faster journeys and more direct services to London."
(LM)
