Victoria Park Tunnel's final lane open today

Motorists heading north through the Victoria Park tunnel can expect the use of a third lane that has been unavailable during the construction process. Photo / Sarah Ivey

The third and final lane of Auckland's Victoria Park Tunnel is opening today, three months ahead of schedule.

As well, the moveable lane barrier on the Harbour Bridge will be extended to the Fanshawe Street intersection during the afternoon peak.

It will provide an additional lane through St Mary's Bay for northbound traffic from 3.30 to 7pm.

New Zealand Transport Agency acting state highways manager Steve Mutton is urging motorists to be cautious and aware of their surroundings.

"These improvements will make journey time in central motorway junction easier and safety, but the traditional northbound queues in peak will continue further south on highway one."

Mr Mutton also says it may take days, or weeks, for the benefits to motorists to kick in.

"We expect delays on the approach to the tunnel to disappear, although it may take a day or two or even weeks for the changes to settle down and for Auckland drivers to really experience the benefits."

A decision on the future use of the Wellington Street on ramp will be made later this year.