A Theiss and McConnell Dowell joint venture has won a contract to build a 5.7km rail line extension to Seaford in south Adelaide, Australia.

The Australia-based construction companies will begin work on the $291m extension later this year.

The work includes building a bus and train interchange, park and ride facilities, three road bridges, and bridges for cyclists and pedestrians.

The project also involves the construction of a 1.2km rail bridge over the Onkaparinga Valley, which would amount to about $250m of the total cost.

Final design and preliminary works the for rail line extension will commence this year, according to adelaidenow.com.au.