Sections of Auckland's Northwestern Motorway will be closed tonight to prepare for new beams to be laid for the complex multi-level traffic interchange under construction at Waterview.

The Transport Agency intends closing all citybound motorway lanes from the existing Great North Rd interchange at Waterview to St Lukes from 10pm until 4am.

There will also be a full westbound closure between the interchange and Patiki Rd from 11pm until 5am.

Both eastbound and westbound on-ramps to the motorway from Waterview will close from 9pm until 4am, although traffic will still be able to travel along Gt North Rd through Waterview to Point Chevelier.

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The closures are to prepare for 60-tonne concrete beams to be laid over the motorway next month, for what will be the highest of four new interchange ramps, 22 metres above the ground.

Two other ramps have already been completed, and the new piece in the jig-saw will ultimately carry traffic from the northbound Waterview tunnel towards central Auckland once a 4.8km link between the Northwestern and Southwestern motorways opens early in 2017.