Network Rail started site work in December on a £45 million project to upgrade the railway route from single to dual line between Swindon, Kemble and Stroud with completion set for Easter 2014.
When commissioned the increased capability will allow the operation of four trains an hour along the line.
This capability will be essential during the planned electrification of the Great Western main line when Bristol Parkway and the Severn Tunnel are closed and South Wales trains are diverted along this route.
Network Rail began enabling works in October and started earthworks at different points along the line in December.
Preparations of the track bed will take place from March to August this year and there will be a 23 day closure of the existing single line between 9 August and 2 September for track alignment.
Work on laying the second line will then take place from September to December, followed in January 2014 by signalling installation and preparatory work ahead of commissioning at the end of April.
Michelle Scogings, scheme senior sponsor, said: “The line of route between Swindon to Kemble was double track up until the late 1960s – a decline in passenger demand led to the singling of the line. Over the intervening years passenger numbers have grown and this scheme will meet the demand forecast over the next 30 years.
“The project has been programmed to coincide with a major signalling renewal which will see the Swindon controls relocated to the Thames Valley Signalling Control Centre in Didcot. This has allowed us to minimise the disruption to passengers.”
Photo top: Looking north from Purton Road bridge where the single line will be dualled this year. Below, the line running from Swindon to Cheltenham at Sparcells