Work to widen key sections of the M25 as part of a £6.2bn contract to improve and maintain England’s busiest motorway officially started today.

The news comes just weeks after the Highways Agency awarded the Design, Build, Finance and Operate (DBFO) contract, one of the UK’s biggest ever transport contracts, to the private sector consortium Connect Plus.

The work to widen two sections of the M25 between junctions 16 and 23 - from the M40 to the A1(M) - and junctions 27 and 30 - from the M11 to the Dartford River Crossing - is being delivered under the contract.

The construction scheme will employ between 3,500 and 4,000 people until 2012 in addition to around 850 people employed on the 30-year operations and maintenance work.

Work to widen the second section - 16 miles of the M25 between the M11 and the Dartford River Crossing - will begin later this month. Both sections are due to be completed before the Olympics in 2012.

Up to 200,000 vehicles a day use the sections of the M25 that will be widened. The work is being phased to reduce the impact on road users and keep as many lanes of the motorway open as possible.