AA bulletins mentioned something about a van broken down near the scene - this hardly would have helped things, and may have been closer to the cause.
Tho, the trains were probably running late on account of the DARTs being disrupted due to a signal fault in Clontarf, which would have altered the paths available for the commuter trains, causing some element of 'bunching' or holding short of services; stack'em, rack'em and pack'em as they say in the airline business.