The state government says its replacement for the Cross River Rail system is a “once in a generation” and “city defining” project.

The LNP has announced a $5 billion dollar combined bus/train tunnel, merging Cross River Rail with Brisbane City Council's Suburbs 2 City bus plan.

The 5.4 kilometre Brisbane Underground tunnel will run from Dutton Park in the south, past new stations at Woolloongabba, George Street and Roma Street, to Victoria Park in the north.

Transport Minister Scott Emerson told Fairfax Radio 4BC that it was an elegant solution to pressing congestion problems on the Merivale Bridge and the Cultural Centre bus precinct.