Traffic is flowing again on Auckland's Northwestern Motorway after a fatal crash closed city bound lanes for more than four hours this morning.

Photo: RNZ/Sophia Duckor-Jones

A motorcyclist died following the crash with a rubbish truck at 6.40am this morning by the St Lukes off-ramp.

SH16 NORTH-WESTERN MWY - SERIOUS CRASH - 7.15AM#SH16 remains CLOSED for all EB traffic between Western Springs off-ramp & Western Springs on-ramp due to a crash. Traffic is being diverted at Westren Springs off-ramp & will be put back onto Mwy at the Western Springs on-ramp. ^MF pic.twitter.com/sqXdlZH6XP — NZTA Akld & Nthlnd (@NZTAAkl) July 1, 2018

Police closed all city-bound lanes while they investigated.

Thousands of commuters were caught in queues backed up for several kilometres on three motorways and surrounding roads.