The new tunnel replaces earlier plans for the $A 5.2bn Cross River Rail project, which was cancelled recently after the new Australian federal government withdrew funding support, and a $2.8bn scheme to expand the bus network.

The north-south tunnel will be 5.4km long running from the Exhibition line via Victoria Park and Dutton Park to join the Gold Coast line south of Park Road station. There will be three new underground stations at Roma Street (the city's main station), George Street and Woolloongabba on the south bank of the Brisbane river.

The tunnel will have an external diameter of 15m with buses on the upper deck and trains below. Stations will be designed to accommodate seven-car trains. A new fleet of emus powerful enough to cope with the steep gradients out of the tunnel will be acquired.

The new tunnel is due to be completed in 2020 with services starting 2021.