The Clem7 toll has been slashed to $2 in an attempt to attract drivers to the troubled tunnel.

The new price takes effect on Thursday and will run until the end of September. It is more than 50 per cent below the price of $4.28 advertised before the tunnel opened in March.

Last month an average of 23,746 vehicles used the tunnel on weekdays, while an average of 21,424 used it on a seven-day average.

RiverCity Motorway originally predicted 60,000 vehicles a day would pay to use the tunnel after a settlement period.

A clearly disappointed RiverCity Motorway CEO Flan Cleary today said he hoped the new reduced toll would attract 30,000 vehicles a day by the end of September.