Environment Minister Amy Adams says that the proposed expressway through the Kapiti Coast is to be referred to an independent board of inquiry.
Transport Agency officials want a four-lane, 16 kilometre stretch of road carved through mainly urban land between MacKays Crossing and Peka Peka.
Ms Adams says the proposal involves significant natural and physical resources and the ecology of the region, as well as its communities and cultural landscapes, could be affected.
She says the board of inquiry process will enable affected people to have their say but will deliver a decision within nine months.
Part of the planned Wellington Northern Corridor, a four-lane expressway from Wellington Airport to about 10km north of Levin, the road is estimated to cost up to $2.7 billion.
Projects contributing to the 110km Wellington Northern Corridor include Transmission Gully work on inner Wellington streets and tunnels, in addition to the Kapiti Expressway.