Balfour Beatty has picked up two of four major roads and bridges packages being let by the Olympic Delivery Authority.
The four have a combined value of £150 million and represent the bulk of roads and bridge work due to be built in the run-up to 2012.
Simon Wright, the ODA’s infrastructure and utilities director, said: “This is the largest tranche of road and bridge work. They will connect the park and provide the backbone for the Games and the legacy mode.”
Contracts will be signed at the beginning of next month. Work will start on site by the middle of March.
Balfour Beatty, which is due to be named preferred bidder for the showpiece aquatics centre next month, has won the deal to build rail over-bridges, known as Lot 3, as well as Lot 4, which involves building the main stadium area bridges.
Lot 3 includes three land bridges and two road bridges, while Lot 4 includes one road bridge and four footbridges.
Skanska has picked up Lot 1 - Olympic Park North - which includes five km of roads, two land bridges, a road bridge and two underpasses.
Nuttall has won the southern equivalent, which features three km of loop roads, four road bridges, one footbridge plus an underpass.
Mr Wright said construction would take a couple of years and would help contractors get around the site but he added it would not hold other work up.
He added that a host of smaller contracts were up for grabs including off-site coach parks and drop-off zones.
A further two bridge contracts are also due to be awarded later this year. The Wetlands area bridges, which include two -permanent bridges over the River Lea, are due to be awarded this autumn.
And prequalification is due to finish this month for the Central Park footbridge, which has been designed by Irish firm Heneghan Peng and is due to see a shortlist drawn up by May. An award is expected by the end of the year.