The largest-ever scheme to modernise the 1960s signalling infrastructure on the Great Western main line has started.

The £400m improvement will significantly benefit services travelling through Bristol, Bath, Chippenham, Swindon, Didcot, Reading, Newbury and Oxford.

The four-year scheme, once completed, could help cut delays by 50 per cent, thus significantly boosting rail performance.

Around 25,000 minutes of delays on average each year on the Great Western main line are potentially caused by problems with aging signalling equipment.

The major upgrade will also support the 10-year plan to expand services on the Great Western main line, catering to the 51 per cent forecast increase in rail demand by the end of the decade.

In addition, the improvement work is also vital to prepare the signalling infrastructure, so that it is compatible with an electrified railway.