"One minor incident in the wrong place at the wrong time" could cause traffic gridlock in Dublin according to AA Roadwatch's Conor Faughnan.
Mr Faughnan was speaking after emergency waterworks caused gridlock for up to four hours in Dublin yesterday evening.
Speaking on RTE's Morning Ireland Mr Faughnan said: "Yesterday it was emergency roadworks, today it could be truck losing its load but if you put a minor incident like that in the wrong place at the wrong time you will cause 3 and 4 hours worth of problems to 20 - 40,000 people."
Traffic was down to one lane on the N11 at Silverbridge, outside Bray, and traffic was backed up all along the N11 southbound.
According to AA Roadwatch, there were also serious delays reported on the Glenamuck Road, Carrickmines, and on the Ferndale Road as drivers tried to avoid the other routes.
Fine Gael's transport spokeswoman Olivia Mitchell said that the delays were an "indictment" of Garda Traffic Corps management.
"The Minister for Justice assures is there are 714 gardaí in the [Traffic] Corps but they are certainly not in evidence at major junctions and potential hold-ups, and were conspicuously absent yesterday on the Bray Road," she said.
Ms Mitchell called for permanent operation Freeflow-type patrols all year round to be introduced.