The Brisbane Underground bus and train project needs a name - and the Brisbane Underground won’t cut it.

Which is why Lord Mayor Graham Quirk and Transport Minister Scott Emerson have launched a two-week competition to give one Queenslander a chance at "being part of history".

The planned Brisbane Underground bus and train tunnel will feature a double decker design with trains on the bottom and buses on top.

The $5 billion project is one of the state’s largest infrastructure undertakings, but how the 5.4 kilometre north-south dual-use tunnel will be funded is still under review.

"We are still working through that," Mr Emerson said.