RiverCity shareholders may be able to launch a class action against the company responsible for traffic projections for Brisbane's Clem7 tunnel.

Transport planning firm AECOM forecast the tunnel's traffic flow would be more than 90,000 vehicles per day, but the most recent figures say it is closer to 24,000 a day.

The resulting financial jam led RiverCity to be placed in administration earlier this year.

Andrew Watson, from law firm Maurice Blackburn, says the company failed to reveal in its product disclosure statement that it had done earlier modelling which showed traffic volumes at a level that would have made the project economically unviable.

He says many people lost significant amounts of money as a result.

"The unit price was $1 and it's now worth effectively nothing, so people have lost the entire value of their holding," he said.

The firm is continuing its investigations.

An AECOM spokesman said in a statement that "the product disclosure statement clearly described the project risks, assumptions and indemnities".

"Since our services were completed in 2005-06, there have been significant events that have affected the local economy, employment and the behaviour of commuters.

"The projects and traffic modelled in the EIS were different to those modelled and described in the PDS.

"This proposed claim lacks merit and any action taken against AECOM will be defended vigorously."