The New Zealand Transport Agency says plans for Transmission Gully near Wellington are on track and it is pleased to have the Government's firm backing that building can begin in 2014.
Transmission Gully is part of the $2.5 billion project between Levin and Wellington airport the agency says will cut 40 minutes from peak morning travel time.
Prime Minister John Key confirmed on Wednesday that construction will begin in the second half of next year.
He says recent earthquakes in the region have boosted the already strong case to upgrade routes into and out of the lower North Island region.
The agency's Wellington State Highway manager, Rod James, says tenders for the $1 billion Transmission Gully project closed earlier in October.
"Having closed the tenders we're now passed a fairly major milestone in the project, so we're in the process of evaluating those tenders.
"We intend to announce the successful bidder sometime in February, so we're really need to appoint the successful consortium and then we can get on with construction."
The Prime Minister says the 27km route will be open for traffic by 2020.