The, built with £70.9M of government money and £5.9M from Severn Trent Properties, will create a new 1.8 mile dual carriageway to allow the A46 to bypass junction 15 of the M40.
Currently A46 traffic must pass through junction 15, leading to delays on both roads and creating the potential for accidents - so causing drivers to divert to other roads.
"The A46 is a vital North-South route for the region, connecting Coventry with Stratford upon Avon and linking towns across Warwickshire to the M40, which in turn provides a vital link to the South-East," said transport minister Tom Harris.
"By cutting congestion and improving road safety this £70m of Government investment to will bring benefits to regional businesses and to both local drivers and those on longer journeys."
The improvement is expected to start in spring 2008 with construction expected to take around 30 months.