Three lorry drivers have been banned from using the Dublin Port Tunnel due to reckless behaviour.
The disclosure comes amid mounting concern over rampant speeding in the tunnel.
The heavy-goods vehicle drivers were each barred from using the tunnel for a month, according to the National Roads Authority (NRA).
Banning motorists for breaching safety by-laws is the only option available to tunnel operators as there is no enforcement of speeding laws inside the tunnel, which is used by 15,000 vehicles a day.
Gardaí have not been operating a normal speed enforcement regime because it is unsafe for officers or contractors to use speed guns in the tunnel.
There is also nowhere to safely pull in vehicles on the approach to or inside the 4.6km-long tunnel.
Details of the bans emerged after a parliamentary question on the issue was tabled by Fine Gael TD Fergus O'Dowd.
Mr O'Dowd said the bans only served to illustrate the need for proper traffic law enforcement in the tunnel.
"The proportion of drivers breaking the speed limit in the tunnel is frightening - and there simply needs to be proper regulation," he said.
"It is particularly concerning when you consider many heavy goods vehicles carry combustible material. I believe we have been very lucky to escape any serious incident so far."
The bans were imposed under tunnel by-laws which forbid drivers from causing danger to any person or property.
The tunnel's operators contacted the companies whose trucks were involved to inform them of the bans.
"They manage the matter internally. That is basically our enforcement. We don't have the powers of the garda," said an NRA spokesman.
The bans were issued in February and September 2013 and in July of last year.
Gardaí are developing plans to fine and prosecute motorists flouting the law in the tunnel.
However, it could be some time before these measures come into force. The tunnel is equipped with cameras which can gauge the speed of vehicles. But these are not suitable for use in prosecutions.
Data from November of last year showed seven out of every 10 vehicles exceeded the 80kph speed limit in the tunnel's south bore. Almost 45pc of motorists using the north bore were clocked driving above the same speed limit.
Although garda speed enforcement is also not carried out within tunnels in Cork and Limerick, neither have experienced the same speeding problems as in Dublin.
The tunnels in Cork and Limerick are considerably shorter and traffic approaches at lower speeds.