National has also promised to work with the council to speed up development of the Eastern Busway, Northwestern Busway and a mass transit solution between the city's CBD and airport.
Bridges also committed a fourth-term National government to starting construction on the proposed $1.85b East-West Link State Highway, building a third main rail line and extending rail electrification to Pukekohe.
English told reporters the decision to take over the Mills Road project was part of an ongoing discussion with Auckland Council.
"Also upgrading it to a State Highway would mean Auckland would have two entrances from the south," he said.
Asked whether the party was focusing too much on roads, English said National had committed to partly funding the Auckland's $3.4b City Rail Link as fast as possible and was also working on improvements to buses and rail across the city.
"It's quite balanced between dealing with the growing volume of traffic and at the same time as investing in the growing patronage of public transport," he said.
NZN