A £5m plan to upgrade a rural railway line linking mid and south west Wales with England has been unveiled by Network Rail which would involve the replacement of a number of passing loops so trains can pass without being held up on parts of on the Heart of Wales Line.

The 120-mile route is weaves its way through some of the most unspoiled and remote parts of Wales.

The work is expected to take place between October and spring next year. Plans are to replace five sets of passing loop points at Knighton, Llandrindod Wells and Llanwrtyd Wells in Powys, and at Llandovery and Llandeilo in Carmarthenshire.

A Network Rail spokeswoman said: "Passengers on the Heart of Wales line will see a marked improvement in train performance as our investment will provide for a more reliable and robust service.

Brecon and Radnorshire AM and leader of the Liberal Democrats in the Welsh assembly, Kirsty Williams, said the improvements were "desperately needed" and added: "This is very welcome news for the much beleaguered Heart of Wales Line.

"I will be keeping a close eye on the situation to ensure that this work does go ahead according to schedule. I have also raised concerns with Network Rail over the safety of level crossings, the need to upgrade phone lines, improved maintenance standard which I hope will be addressed."