The UK Highways Agency will upgrade the A23 road in West Sussex between Handcross and Warninglid, as a part of a £1.4bn funding grant, which includes 14 improvement schemes.
The agency will widen the A23 road by adding three lanes in each direction to improve safety, reduce travel times and to ease traffic congestion on the road.
The A23 project team is already on course to save about 23% of the cost against the previous estimates.
UK Roads Minister Mike Penning said that investing in transport infrastructure will help the economy grow.
"The improvements being made here will tackle congestion that affects drivers on the A23 every day," Penning added.
"The savings the Highways Agency has negotiated means the scheme will deliver an estimated £8 worth of benefits for the UK for every £1 we're investing.
"There will be real safety benefits too - by straightening out the road and improving the junctions the scheme will reduce the number of severe accidents that have come to blight this section of the road network.
"The savings have been achieved without sacrificing the project's environmental credentials."
The agency is expecting to start the main civil engineering work on 2 July 2012 and environmental work has been underway on the site since April 2011.
The Highways Agency is an executive agency of the UK's Department for Transport and it manages, maintains and improves England's motorways and other strategic roads.