Auckland drivers will be able to use the Victoria Park Tunnel from November, two months earlier than planned.

Transport Minister Steven Joyce said today the NZ Transport Agency's $340m project to ease motorway congestion in the central city was heading towards an early finish.

"Firstly the entire project is now on track to be finished by February next year, which is a year and three months earlier than expected.

"Secondly, the first two northbound lanes will be opened in November, which will move the traffic around so the rest of the project can be finished," Mr Joyce said.

Work on the 450 metre-long tunnel was progressing very well, he added.

"The walls have been completed, the roof is on, and about 80 per cent of the excavation is now completed.

"It will greatly ease congestion for the 160,000 plus vehicles that use this route each day," Mr Joyce said.

The entire project includes the widening of State Highway 1 through St Mary's Bay and the reconfiguration of the existing Victoria Park viaduct to carry four southbound lanes of traffic.

NZTA's State Highways Manager for Auckland, Tommy Parker, said the key to the tunnel's early opening was the planned closure next month of the Wellington Street on-ramp, which links the central CBD with the northbound lanes of SH1.

During the seven month-long closure, a new on-ramp will be built and construction of the southern portal of the tunnel completed.

The Victoria Park Tunnel project is the first of the Government's seven roads of national significance, to start construction.

It aims to support economic growth by reducing congestion, improving safety and journey times, and increasing the capacity of State Highway 1 between the Auckland Harbour Bridge and Newmarket, one of the country's busiest freight and business routes.

- NZPA