Highways England awarded the deals under its Regional Delivery Partnerships framework.
The £300m A47 contract and £135m A303 Sparkford to Ilchester deal are the biggest contracts awarded under the framework since it was announced last year.
Peter Mumford, Highways England Major Projects Executive Director, said: “This is clear evidence that new ways of working are being embraced by the market, which is now seizing the opportunity to work in a more integrated way with us, representing a fundamental change in the way we deliver our road projects.
“We will continue to work with the supply chain and look forward to completing and announcing more contracts in due course.”
The deals have been set up using the Routes to Market Regional Delivery Partnership, with the 13 companies – known as Delivery Integration Partners (DIPs) – working on 18 packages of schemes across the country.
Duncan Elliott, Managing Director of Galliford Try Highways, said: “We’re delighted for this opportunity to further strengthen our relationship with Highways England in schemes which will bring such a huge benefit to their customers.
“The appointment underlines the strategic importance of highways to our construction business and the vast experience, expertise and resource we can offer in this sector.”
The A47 improvement programme is scheduled to be completed in 2024 with work set to start on the A303 Sparkford to Ilchester scheme next March.