The Queensland Government has unveiled plans for a new $5 billion public transport tunnel in Brisbane.

The 5.4 kilometre tunnel will link Dutton Park to Bowen Hills and include a station at Woolloongabba and another at George Street in the city.

The double-decker tunnel will see trains operating on the bottom level with buses on top.

Transport Minister Scott Emerson says the Underground Bus and Train (UBAT) tunnel will solve many congestion issues.

"It is a once-in-a-generation and really a city-defining project for Brisbane," he said.

"By combining the projects and also putting that station in George Street we do get a really great outcome for public transport users while giving a really effective use of taxpayers dollars."

He said the current option is much more affordable than previous ones.

"There were a number of projects already out there previously. They were very expensive and unaffordable," he said.

"The previous projects had price tags of more than $5 billion for the rail and almost $3 billion for the bus.

"This project will cost $5 billion - $3 billion less than those other projects would have cost taxpayers."

Mr Emerson says construction will start in 2015 and be completed six years later.

RACQ's Michael Ross has welcomed the plan, saying it will be a much-needed solution for train and bus congestion in the city.

"All these projects take a long time. There's a lot of detail in there and there's a lot of work," he said.

"In the middle of the city it's very difficult to build such large infrastructure, so we always knew it would take a long time.

"Most train tunnels are done with a much smaller tunnel, just to fit one train line in them each.

"They've gone for a design with a 15-metre-wide bay tunnel - so a very big tunnel and trains on the bottom level and buses on the platform above.

"It's great to see the government has announced it is going to push ahead with it."

Private sector support will be sought

The Queensland Government says it is investigating ways to fund the tunnel.

Treasurer Tim Nicholls says the Government will ask the private sector to be involved.

"We can certainly be looking at infrastructure bonds," he said.

"There are wraps made available, financing tools that are made available that are much more innovative than simply just going out there and asking for the Government to pay for it. So we need to investigate those areas.

"We know that there's an appetite in the market to be part of what Government delivers, that's why we'll be speaking to the people in Projects Queensland about how we can go about delivering this in the most efficient and economic way."