A European Court ruling could force the Republic to accept so-called super-trucks on its roads, despite Taoiseach Bertie Ahern's insistence that they are "not needed".
The European Court of Justice last week overturned a local government regulation in Austria banning lorries of over 7.5 tonnes from a 46km stretch of motorway in that country's Tyrol region.
The court ruled that the ban, introduced by Tyrol's regional government on environmental grounds, obstructed the free movement of goods between EU member-states, and was illegal under European law.
The Austrian ban included the so-called "super-trucks" that cannot fit into the Dublin Port Tunnel and which the Taoiseach said recently should be "turned around and sent back".
Super-trucks will not fit into the tunnel when it is opened next year as it does not have the 4.65 metre clearance that they need.
However, despite the fact that they are used increasingly in Europe, the Government has consistently ruled out adjusting the tunnel to accommodate them.
Mr Ahern said that the trucks were an unnecessary development. "Super-trucks should be stopped and sent back out again . . . we don't need super-trucks," he said.
The ruling could also have implications for Dublin Corporation proposals to ban heavy goods vehicles in the centre of the capital during a 12-hour period between 7am and 7pm.
The European Court of Justice made it clear that the Austrian authorities should have provided an alternative for transportation of the goods.
"They [the Tyrol authorities] did not sufficiently study whether there actually was a realistic alternative solution ensuring transportation of the goods concerned by other means of transport or other road routes, and, in particular, whether there was sufficient and appropriate rail capacity," it said.
The only alternative to the Dublin Port Tunnel will be through the city itself. The fact that they cannot go through the tunnel will leave them with no choice but to travel through the city.
The court's ruling was also influenced by the fact that the route in question is a key link between Germany, Austria and Italy.
Dublin Port is the State's biggest entry and exit point for goods that are being imported and exported, and is an important connection between the State and the rest of Europe.
EU law obliges member-states to allow the free movement of goods, services and people between each of them, except where issues such as environmental protection or public health take precedence.
While the European Court of Justice recognised that there was an environmental concern in the Austrian case, it ruled that the steps the regional authority took were out of proportion to the pollution risk posed by the trucks.
