The remains of a former bed for a railway built in 1927 to take trains carrying construction materials from the valley floor railway NPRN 267326, over bridge NPRN 267133 up the west facing, lower valley side, and then along a small section of track laid on the northwest end of road NPRN 267109 to the far end of the Grwyne Fawr reservoir. The railway ran from SO2368030500 via SO2413030230 to SO2255031330. This extra piece of railway became necessary when the tunnel carrying the valley floor railway through the reservoir dam wall was blocked in as the construction work progressed. The track was lifted in 1928 when the reservoir was completed. When visited in September 2007, the railway could be seen as a trackway running up the side of the valley but it was not noticeable along the road segment.
Source: Tipper Rev DA, 1975, Stone and Steam in the Black Mountains, p. 44, plan page 45
J.J.Hall, Trysor, 22 January 2008