Traffic is slow on Auckland's motorways after a series of crashes this morning.

The cars involved in the crashes have been cleared away but the NZTA said delays continued on the Southwestern, Northern and Northwestern motorways.

Traffic is still crawling heading into the city on the Northwestern Motorway after a crash at the end of the Royal Rd on ramp blocked the right lane.

The New Zealand Transport Agency warned people to avoid the area and expect long delays.

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And shortly after 6.30am a crash blocked a citybound bus lane on the Northern Motorway after the Greville Rd on-ramp.

Motorists were warned to take care as buses merged with traffic to pass.

Auckland Transport is also warning of possible ferry and train cancellations and restrictions on double-decker buses crossing the Harbour Bridge because of the winds expected to come with Cyclone Cook.