The existing flat junction poses a constraint to the strategically-important Adelaide - Melbourne line, with freight trains frequently held at the junction to give priority to Adelaide Metro Outer Harbor commuter trains.

The project will grade separate the lines by carrying Outer Harbor trains beneath the interstate rail corridor for a length of approximately 1.4km. The underpass will also remove two level crossings at Gibson Street and Park Terrace, the latter with a daily traffic flow of 50,000 vehicles.

Furthermore, the project will reduce delays for road users at the Torrens Road and Hawker Street level crossings, which are often blocked by freight trains approaching Torrens Junction.

The removal of this bottleneck will improve the productivity of the interstate freight network by enabling the operation of more 1800m-long freight trains between Adelaide and Melbourne.

The opportunity will also be taken to relocate the existing Adelaide Metro Bowden station a few hundred metres to the north, which will improve connectivity with new residential and leisure developments in the area.

The closing date for expressions of interest in the project is August 9.