Work is already underway on the widening of the M25 between junctions 16 and 23 just after a day after the £6.2 billion project reached financial close.
Traffic management will be put in place between junctions 16 and 18 starting next Wednesday (27 May) where the first widening work will take place.
Preliminary work, including site preparation and vegetation clearance, has already taken place.
Work will begin on maintaining the motorway and its structures including the Hatfield Tunnel from 1 June.
Widening work between junctions 27 and 30 will begin on 21 July.
The consortium is split into a contractor joint venture between Skanska and Balfour Beatty as well as a maintenance and renewals joint venture which will begin work in September.
Connect Plus chief executive Tim Jones said: “There will be a whole ranch of sub contract packages that will be let to the market.
“The heavy maintenance and renewals work will be put out to tender by Connect Plus in the next couple of months with an appointment needed to be in place ready for work to begin in September.”
Mr Jones added: “The message is loud and clear. This is a mega deal which will bring the industry together.
“I have been through a number of recessions and in my view the industry always works well in adversity.”
There is potential for a further two sections of the motorway - taking in junctions 5 to 7 and 23 to 27 – to be converted.
The Highways Agency will not make a decision for some time and is understood to be looking at the possibility of hard shoulder running, rather than widening in the traditional sense.