Concerns over the impact of a massive road-building project in Auckland are valid, says the head of the Transport Agency, but the Waterview motorway will go ahead anyway.

Transport Agency chairman Brian Roche said yesterday that his board had confirmed a combined surface-tunnel option for the 4.5km route, which will destroy up to 365 homes and five hectares of green space.

That followed its consideration of a litany of community presentations against the $1.4 billion project at a meeting in Mt Albert a fortnight ago, at which he said "they certainly left us in no doubt as to the consequences".

"There were very strongly held views by the community which we fully understand - they are very valid concerns and we appreciated the fact that people were able to articulate them," Mr Roche said.

But he said the completion of Auckland's 48km western ring route, of which Waterview remains the final major missing link, was crucial for the national economy as well as the region's transport network.

Subject to board approval in November of a final design for the motorway, Mr Roche said the agency would lodge a land designation application early next year with Auckland City, for a construction start in 2011-12 and completion in 2015.

Mt Albert Labour MP David Shearer said: "National's cut and cover option lacks vision and sense - it doesn't take into account the wishes of a community that will now be split in two."