Mr Dillon submitted to the board that north-facing ramps should be added, and a second interchange be built on Moirs Hill south of Warkworth, on land which the agency intends acquiring from his client Asia Pacific International.
He claimed the agency was reluctant to provide intermediate entry and exit points to the motorway as that would make it easier for drivers to avoid paying tolls.
But the chairman of the five-member board, retired High Court judge John Priestley QC, said overseas tolling systems were sophisticated enough to keep tabs on drivers leaving and joining the motorway.
Mr Dillon said Moirs Hill would be an ideal location for an interchange and service centre, as the agency wants to widen the local road there for motorway construction traffic.
It would take pressure off Warkworth's difficult turnoff to eastern beaches through the Hill St intersection by allowing residents to join the motorway south of the town rather than having to head north to a new roundabout at the end of the extension.
Yesterday's hearing session began with Mr Priestley suggesting the agency consider "what should become of Hill St", given local concerns about its intention to delay an upgrade of the intersection until the motorway is completed in about 2021.
Campaign for Better Transport convenor Cameron Pitches told the inquiry Hill St would come under increasing pressure even after the motorway is built, as agency computer-modelling predicted more traffic would continue to use the existing State Highway One through Warkworth by 2026 than what the new road was expected to carry.
That was without considering the impact of tolls, which would encourage even more drivers to stay on the old road, especially as it would remain a faster route to the eastern beaches than the motorway.
The main time savings would be for drivers heading further north, and his group's preference was for an 8km bypass Warkworth costing about $50 million.
That and safety upgrades on Schedewys Hill and the Pohuehue Viaduct would be at least $500 million cheaper than building a four-lane motorway not carrying enough traffic to justify the cost.
Mr Pitches said the savings could be used on more useful projects further north, such as in the Dome Valley or over the Brynderwyn Hills.
He acknowledged to Mr Priestly that the existing highway between Puhoi and Warkworth was a difficult stretch, but said travel times were generally "not that bad" other than during holidays.
Luke Christiansen of the Generation Zero youth organisation said it was surprising the road-builders had not presented any data to the inquiry to show how the motorway would fulfil one of their stated objectives for the motorway, of stimulating Northland's economy.
