The Transport Umbrella Group (TUG) is to present its proposals for alterations to the height of Dublin Port Tunnel at an Oireachtas committee today.
The group, which represents wide range of hauliers, ferry operators, exporters and Dublin Chamber of Commerce, is to address the Joint Transport Committee.
It is expected to propose increasing access for "supercube" trucks to the €625 million tunnel.
This would involve changing the width of footpaths along the carriageway to make trucks travel closer to the centre of the tunnel, where the roof is higher.
This would raise the clearance from 4.65 to 5.05 metres and could be achieved at very little extra cost to the project, according to the TUG.
The National Roads Authority and Dublin City Council have dismissed the suggestion, arguing that it would pose too high a safety risk to have such large vehicles travelling so close together.