Auckland motorists have been asked to be patient as major upgrade projects start on both the Southern and Northwestern motorways this weekend, causing closures on both routes.

The Great North Rd on-ramp to the Northwestern Motorway, westbound, will be closed from 8pm today until 5am Monday.

The on-ramp will be moved slightly to the south to create working space for motorway upgrade work.

Drivers are advised to use alternative routes, and diversions will be signposted to St Lukes and Patiki Rd, where bus services will be re-routed.

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City-bound drivers will not be affected, and the northwestern cycleway remains open.

The work is part of the causeway upgrade project, which will raise and widen SH16 from Great North Rd to the Whau River Bridge near Te Atatu.

On the Southern Motorway, city-bound lanes will be closed from the Ellerslie-Panmure interchange to Greenlane from 10pm on Sunday to 5am Monday.

The work is part of the SH1 Ellerslie widening project to build a fourth lane, which is due for completion mid-2016.