It would help Northland's economy grow by getting people to work and freight to key export markets more quickly.
The straighter road was expected to reduce deaths and serious injuries due to crashes by 80 per cent.
Mr Bridges said the motorway would reduce through traffic in towns such as Wellsford by 90 per cent, making then safer for local road users and cutting reducing noise and pollution.
No decision had been made on tolling. NZTA would protect the route by applying for consents by the end of 2018.
While many residents will welcome the reduction in traffic along the current SH1 some businesses, especially along Wellsford's main street, depend on it for their livelihoods.
The current SH1 also passes tourist attractions such as SheepWorld, just north of Warkworth, and the Maori cultural village Te Ao Marama at Te Hana.
However, SheepWorld manager John Collyer said the benefits of the Puhoi-Warkworth motorway extension, which would bring the sheep-themed attraction closer to where most of its visitors came from, would outweigh any disadvantages of the Warkworth-Wellsford stage.
Te Ao Marama chief executive Thomas de Thierry said "very few" of the village's visitors were spontaneous passers-by.
As long as cultural sites were protected during motorway construction it would "best for everyone" to see traffic congestion fixed at Te Hana and Wellsford.
The entire Ara Tuhono Puhoi-Wellsford Road of National Significance is expected to cost $1.76 billion, with the Warkworth-Wellsford stage accounting for about $1 billion.