The spokeswoman said Transport minister Noel Dempsey was "hopeful" of introducing the tough new measure before the end of the year as part of its efforts to combat the increasing number of costly bridge strikes by large trucks over the last few years.

The department has warned that such incidents "have the potential for major catastrophes".

The measure is already included in the Road Safety Act, 2006, but gardai need to be administratively prepared to enforce the measure before the minister can introduce the commencement order.

And in a further bid to minimise bridge strikes, last January, former minister Martin Cullen announced his intention to introduce a new national maximum vehicle height of 4.65m . . . the same maximum height that applies at the Port Tunnel.

But the measure, which was the subject of widescale public consultation, has to be referred to the European Commission first. The country did have a national maximum height restriction of 4.25m between 1991 and 2000, but the EC ordered it be scrapped as it prevented some 'super trucks' operating in Ireland.

Nationally, six rail bridges exceed 4.6m and 19 are equal or below that height. In Dublin, 29 bridges are over 4.6 and 20 are under, while in Cork four are over 4.6m and two are under.

The city-centre bridge at the centre of the case has been dubbed the "most struck bridge in Dublin" by Iarnrod Eireann's Barry Kenny.