Aucklanders have been warned to expect delays as tractors and utes head south following a protest in the city centre.
A serious crash has also closed the northbound lane at Mangere's Coronation Rd and an incident involving a truck losing its bin near Mercer has delayed southbound travellers.
Waka Kotahi, New Zealand's Transport Agency, said traffic was "very heavy" on the southern motorway at 2pm and advised motorists to delay their journey or consider using State Highway 20 as an alternative route to Manukau.
UPDATE 3:15PM Traffic remains slow southbound on the #SouthernMwy however most slow vehicles are now clear of Auckland's motorways. Allow extra time for journeys this afternoon with Friday afternoon's peak travel time now beginning. ^TP https://t.co/NrFiJSpINm
— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) July 16, 2021
At 2.30pm, Waka Kotahi confirmed southbound traffic was still moving slow from the city centre to Papakura. Motorists were advised to allow extra time for their journey.
The most recent update said most of the slower vehicles were clear of motorways but traffic was still slow.
The Howl of a Protest event, organised by Groundswell New Zealand, has seen thousands of farm vehicles rumbling through cities in protest against what farmers say is increasing interference from the Government, unworkable regulations and unjustified costs.
The protests are taking place in 55 cities starting from Kaitaia to Southland.
Hundreds of farmers have hit Auckland CBD after taking to the Southern Motorway in tractors, heavy farm equipment and utes to participate in the protest.
SH20 CORONATION RD ON-RAMP CLOSED - 2:55PM Due to a serious crash the on-ramp from Coronation Rd to SH20 Northbound is currently closed. Please follow the diversion to Rimu Rd for access to SH20 northbound. ^TP https://t.co/LfFxXJwphg
— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) July 16, 2021
The area around Drury and Ramarama was gridlocked at 9.30am as the convoy made its way to the motorway. It appeared motorists would face similar delays heading south this afternoon.
Elsewhere, NZTA warned commuters that the on-ramp from Coronation Rd to SH20 northbound in Māngere is currently closed after a serious crash.
Motorists should follow the diversion to Rimu Rd for access to SH20 northbound.
UPDATE 3:00PM This crash still blocking southbound lanes on #SH1 with vehicle recovery well underway. Long delays are occurring southbound from Pokeno to Mercer. Delay your journey or allow extra time. ^TP https://t.co/W7gkVhP4Li
— Waka Kotahi NZTA Waikato/BoP (@WakaKotahiWaiBP) July 16, 2021
Further south, a truck has reportedly lost its bin near Mercer, causing kilometres of backed up traffic heading south.
Meanwhile, SH1 between Oteha Valley Rd and Silverdale will be closed between 9pm-5am for maintenance in three four-day periods.
They would be from July 18-21, August 1-4 and August 9-12. The maintenance was weather dependent and could be rescheduled for late July and early September.
A detour along Dairy Flat Highway would be available. The BP Service Station at Dairy Flat and other shops on SH1 will be closed.