Cafwyd yr adroddiad cyntaf bod y system signalau wedi methu ym Mlwch Signalau Caerdydd Canolog am 07:07. Wedi hynny, daeth cadarnhad fod blychau signalau Cyffordd y Mynydd Bychan a’r Barri wedi colli pŵer hefyd.
The first report that the signalling system had failed was received from Cardiff Central Signal Box at 07:07. Subsequently, Heath Junction and Barry signal boxes confirmed that they too had lost power.