Keep left at motorway exit, Transit warns city drivers

Final touches are being put to the new Nelson St off-ramp, which will open early on Monday. Picture / Paul Estcourt

Motorists taking the Southern Motorway into central Auckland should watch out for a major off-ramp change from next Monday.

Drivers will use a new off-ramp to Nelson St on the left-hand side of the motorway instead of the existing ramp on the right. Immediate results are expected to include greater safety and less traffic weaving and changing lanes.

The new off-ramp, which runs along a new eight-span viaduct about 250m long, is due to be opened in the early hours of Monday.

Transit NZ will place large signs on the Southern Motorway giving warning of the change. Motorists using the present off-ramp are being handed pamphlets explaining the changes as they stop at the Nelson St lights.

Traffic engineers say there will be one immediate benefit for the large amount of northbound traffic that enters the motorway at Gillies Ave, then exits at the nearby Nelson St off-ramp. Achieving that at present means weaving across some of the country's busiest motorway lanes to reach the right-hand exit.

The full benefit of the change will come in a few months when further works, including upgrading crash barriers on existing bridges, are completed. City-bound traffic will then have room to get into a left-hand lane leading to the off-ramp sooner. And traffic in the Southern Motorway's two right-hand lanes should have a freer run down towards Victoria Park and the Harbour Bridge.

The new off-ramp structure includes much stronger crash barriers. They are also topped with a heavy-duty rail to ensure that even large trucks cannot topple on to motorway lanes below.

The new off-ramp will be marked as a 3.5m single lane from the beginning of the exit, allowing a 2.5m emergency shoulder on the western side in case of breakdowns or accidents.

Nearer Nelson St, this lane will branch into four lanes, allowing better flow through the Nelson St traffic lights, including one left-turning to Union St.

The existing right-hand off-ramp built in the 1970s will be kept for emergency vehicles.