Designers of Auckland's $2 billion Waterview motorway tunnels project are trying to solve congestion and safety problems at a three-tiered interchange between two state highways.
Among 12 options under consideration are shifting Great North Rd to the west through Waterview, and then sending it over the new motorway interchange en route to Pt Chevalier, instead of under it.
The Transport Agency said these were only preliminary ideas, with no formal standing.
But they had to be refined into a short-list before decisions could be made on whether to deviate from an earlier proposal presented to a Government-appointed board of inquiry.
The agency's northern highways manager, Tommy Parker, acknowledged that moving Great North Rd westward through the Waterview straight, to allow traffic to emerge from a motorway tunnel on the eastern side, would have "huge implications".