The chief executive of Dublin Port Company has said new customs checkpoints in the port - the first to be built here in decades - will be a pinch point.
However Eamonn O'Reilly said he does not think the new border inspection posts will cause congestion, although there are likely to be delays.
He said he believes the necessary technology is in place and Revenue already runs an efficient operation at the port, dealing with goods coming from third countries.
Third countries are all those that are outside of the European Union, the European Free Trade Association or the European Economic Area.
Mr O’Reilly said the checkpoints would absolutely act as a pinch point because that is "what Brexit is all about".
"We've had free trade up to this since the 1990s," he said. "Goods must now pass through these sorts of checkpoints."
Mr O'Reilly was speaking to RTÉ News after it was given access to film the new customs checkpoints for the first time.
"We saw these sorts of control points disappear in the early 1990s," he said.
"They do remain in place for the trade coming through our three container terminals, where you've got containers coming from China.
"So there is nothing new in what we are seeing, we are just seeing a far greater scale."
At present around 200,000 trucks, lorries and containers arrive in Dublin Port from outside the EU each year.
Mr O'Reilly said that if there is a hard Brexit on 29 March, that number will jump overnight to one million a year as the UK becomes a non-EU state.
Read more:
British PM says parliament can vote on any Brexit delay
Potential Brexit extension an 'important development'
Govt allocating €428m to Brexit preparations this year
Dáil begins debate on no-deal Brexit legislation
He said the port is as ready as it can be for that eventuality, and that all the booths will be finished by that date.
90% of freight arriving into and leaving Ireland via roll-on-roll-off ferries comes through Dublin Port.
If Brexit takes place, truck drivers will use an online system to file details of their load with customs and should know before they land whether they have been designated green, amber or red.
They will then pass through one of the new customs checkpoints and either be sent on their way if customs officials are satisfied, or they will be sent to other parts of the complex for further inspections.
Mr O'Reilly said there should be no reason for delays as the systems are well understood by all involved in using them.
But he added that the one big concern is whether there will be enough state officials in place that will be needed to process the freight.
He said it was a high ask for the state to be 100% ready for 29 March and there will probably have to be a ramping up of the inspections required by the EU over time.
By the end of March, Dublin Port will have spent €30 million on Brexit preparations.
Mr O'Reilly said much of that money would have been spent anyway in years to come, and has just been brought forward for Brexit.
