Work has begun on Wales’ largest congestion-busting scheme to potentially provide hundreds of extra rush-hour seats each day on rail services on the Cardiff and Valleys’ network.

Due for completion by 2015, this £220m scheme, with funding of £17m from the Welsh Government, will deliver a bigger, better railway for the Cardiff and Valleys’ network and will support the growth of the local economy.

The work will be delivered in five stages, starting with the Vale of Glamorgan line.

The three-year programme will mobilise hundreds of railway workers to replace over 300 signals, 12 miles of track, 59 sets of points and build seven additional platforms across the Cardiff and Valleys’ rail network, including at Barry, Caerphilly, Pontypridd and Tir-Phil stations.

The scheme will remove the rail bottleneck between Cardiff Central and Queen Street, allowing 16 passenger trains per hour to run through the area – a 25% increase. The extra capacity will also allow more freight trains to run through Cardiff helping to support businesses in their transport of goods to and from Wales.

Cardiff Central (south side) and Cardiff Queen Street will also see new entrance buildings and facilities to improve passengers’ travel experience. These stations account for 67% of all passenger demand on the South Wales Valleys’ network and cater for almost 12.5m passengers every year.

The work is an important first step towards electrifying the Valleys’ network. The recent decision to fund the electrification of the network was based on a business case that offered the increased capacity that these improvements provide.

A new station will also be built to serve the growing community at Energlyn.

Mark Langman, route managing director for Network Rail Wales, said: “We need to expand today’s railway to cater for tomorrow’s needs, and we are getting ahead of the game. Through this investment, passengers will significantly benefit from the potential to run more services and a better performing railway, which is also vital to support Cardiff as a key economic centre for Wales.

“The city has the largest travelling workforce in Wales with around 37% of the workforce commuting from neighbouring authorities, in particular, from the Valleys. A large number of that workforce relies on rail and usage is expected to increase by 8% on average each year, adding further demand on an already-congested railway.

“On a network as busy as ours, this work is the equivalent of conducting open heart surgery on the railway whilst keeping daily services running with the minimum of disruption”.

Welcoming the launch of Network Rail’s Cardiff area re-signalling renewal project the Minister for Local Government and Communities, Carl Sargeant, said: “This multi-million pound investment, which includes Welsh Government funding, will allow additional capacity on the rail network around Cardiff.

“This is the first tangible step in delivering electrification of the Valley Lines, as well as part of the continued investment and improvement of the rail network in Wales, as set out in the National Transport Plan.”

Mike Bagshaw, commercial director for Arriva Trains Wales, said: “This important work will lay the foundation for future extra capacity and will mean extra services and journey opportunities for passengers using one of the busiest parts of the Arriva Trains Wales network.

“When combined with the recent electrification announcement, station improvements being delivered by Arriva Trains Wales and Network Rail, and the extra capacity the project will deliver, passengers in the Cardiff area will see a real transformation to their rail services.”

To minimise disruption, the work over the next three years will be mostly carried out at night when trains are not running. In addition, innovative techniques will be adopted - such as the use of lightweight signals to reduce installation time whilst achieving cost-savings.

With the 1960s signalling system completely modernised, rail services will also become more reliable and compatible with an electrified railway.

The contractors appointed to carry out the work are Atkins, Siemens, Balfour Beatty, Birse and Bam Nuttall.