PwC will assist the agency in structuring and procuring the two initiatives, which are expected to involve a design-build-finance-maintain model.
Under current plans, works for the £1.3bn A303 project will involve the delivery of a 2.7km tunnel under the Stonehenge World Heritage Site, a bypass for Winterbourne Stoke and improvements to junctions between the A303 and the intersecting A345 and A360.
With a capital expenditure of approximately £1.5bn, the Lower Thames Crossing PF2 is expected to enter the development phase shortly, followed by the development consent order stage for procurement to start later on.
Works for that project involve a tunnel between the River Thames east of Gravesend and Tilbury, with new link roads to the M25 north of the river between junctions 29, 30 and to the A2 south of the river east of Gravesend.
Highways England launched the search for financial advisers for the PF2 schemes during the summer.