Passenger traffic through Colbren would begin its decline following implementation of the railway groupings in 1922.
The Midland and the London and North Western Railways (L&NWR) each became part of the new London Midland and Scottish Railway (LMS), while the Neath and Brecon (including the Ynys-y-Geinon branch) passed to the Great Western.
These changes meant the original purpose of the Midland’s route into South Wales was now annulled because the new LMS company could now send all its South Wales traffic via the former L&NWR Central Wales line.

LMS passenger trains between Brecon and Swansea continued to stop at Colbren Junction until 1930.
This service was then replaced by Brecon to Neath trains operated by the GWR.
A short-lived passenger service continued to use the branch to Ynys-y-Geinon for a further two years; until finally ceasing in 1932.
Subsequently both platforms on the Swansea branch fell into disuse except for occasional excursion trains.

The passenger service between Brecon and Neath was finally withdrawn in October 1962; by now it had been reduced to one train per day in each direction.
In 1966, the direct lines linking Neath and Swansea with Brecon via Colbren were deemed to be no longer viable.
The Swansea branch to Ynys-y-Geinon ceased carrying local freight in 1967 wherein Colbren stopped being a junction with the removal of the branch.
Freight traffic continued to pass through Colbren from Penwyllt quarries to Neath until 1977.
Following the removal of the track through Colbren, the Neath and Brecon line now terminates at the coal washer at Onllwyn.

Little remains at Colbren of the station or the junction; although surviving conifers indicate the alignment of the track of the former railway.
Passenger traffic through Colbren would begin its decline following implementation of the railway groupings in 1922. The Midland and the London and North Western Railways (L&NWR) each became part of the new London Midland and Scottish Railway (LMS), while the Neath and Brecon (including the Ynys-y-Geinon branch) passed to the Great Western. These changes meant the original purpose of the Midland’s route into South Wales was now annulled because the new LMS company could now send all its South Wales traffic via the former L&NWR Central Wales line.
LMS passenger trains between Brecon and Swansea continued to stop at Colbren Junction until 1930. This service was then replaced by Brecon to Neath trains operated by the GWR. A short-lived passenger service continued to use the branch to Ynys-y-Geinon for a further two years; until finally ceasing in 1932. Subsequently both platforms on the Swansea branch fell into disuse except for occasional excursion trains.
The passenger service between Brecon and Neath was finally withdrawn in October 1962; by now it had been reduced to one train per day in each direction. In 1966, the direct lines linking Neath and Swansea with Brecon via Colbren were deemed to be no longer viable. The Swansea branch to Ynys-y-Geinon ceased carrying local freight in 1967 wherein Colbren stopped being a junction with the removal of the branch. Freight traffic continued to pass through Colbren from Penwyllt quarries to Neath until 1977. Following the removal of the track through Colbren, the Neath and Brecon line now terminates at the coal washer at Onllwyn.
Little remains at Colbren of the station or the junction; although surviving conifers indicate the alignment of the track of the former railway.
Colbren Junction railway station