The JV saw off rival bids from Laing O’Rourke, Balfour Beatty/Alfred McAlpine and Carillion/Nuttall for the early contractor involvement deal to upgrade the A14 between Ellington and Fen Ditton.
The deal was valued at up to £678 million when it was advertised in February last year.
The Costain/Skanska team will be responsible for designing the whole project but will only carry out the widening work between Fen Drayton and Histon. The other elements of the scheme will be subject to separate tendering exercise upon completion of statutory processes.
Construction is expected to start on site in late 2010 and to be completed in stages between 2012 and 2015.