Great Western Main Line electrification begins
13 August 2014 Last updated at 08:50 BST
Work to electrify the Great Western Main Line has begun.
Network Rail is using a specially-designed factory train called Brunel which works at night so trains can keep running during the day.
The train works up to five times faster than conventional gangs of track workers.
The team will work westwards at one mile a night, reaching Oxford, Newbury, Swindon and eventually Bristol and south Wales at the end of 2016.