Cymmer Viaduct linking the L&OR and the SWMR was opened in July 1878. After the closure of Gyfylchi Tunnel due to a landslip in July 1947 the viaduct became the only route out for traffic on the former SWMR north of Cymmer Corrwg. The viaduct was never passed for passenger traffic meaning that stock for the Cymmer Corrwg-North Rhondda workmen’s trains and the occasional railtour had to cross over empty.
My question is: what and how much revenue traffic passed over the viaduct between 1878 and 1947? All I have found out so far is the following in the GWR STT for May 1911:
LAND SALE CÓAL TRAFFIC, CYMMER (EX R&SBR AND SWMR LINES) TO THE LONDON DISTRICT, FOR MESSRS. BRADBURY, AYRES, Wm COREY AND SON, ETC. Special efforts must be made to get this important and valuable traffic away from Cymmer by the 7.30 p.m. minera1 train thence to Maesteg, and 9.35p.m. Maesteg to Cardiff, to connect with 8.15 a.m. Penarth Junction to Swindon.
This is not particularly explicit as the ex-R&SBR traffic would not have crossed the viaduct, it just requiring a shunt through the exchange sidings with the GWR at Cymmer.
The SWMR WTT of March 1918 makes no mention of traffic across the viaduct.
Any further information of this subject would be most welcome.