City authorities in South Korean capital city Seoul are planning to build underground highway tunnels at an estimated cost of US $9.14bn under a new project to tackle traffic congestion.

The project envisages construction of six underground highways across 149km, of which three will run east-to-west routes and the other three north-to-south.

Developers constructing routes one and two of both east-to-west and north-to-south directions are expected to be selected in 2012 and the work on these routes is likely to be finished in 2019.

The design works for route three will begin in 2010 with completion targeted for 2017.

Private firms will be called to finance the tunnels project and the tunnels will run 40-60m below the surface.