SH20 is congested from Lambie Drive to Māngere Bridge.
"Consider delaying your journey, using an alternative route or allow extra time today,'' a statement said.
SOUTHERN MOTORWAY:
An update from NZTA at 8.15am said traffic on the Southern Motorway was heavy between Drury and Takanini and moderate to heavy through Te Irirangi Drive, Princes St and Mt Wellington.
Southbound, traffic is heavy between Newmarket and Mt Wellington.
A police spokeswoman said three vehicles were involved in the Māngere Bridge crash and no injuries were reported.
Motorists passing through the area are being urged to drive with extra precaution and to expect delays.
That collision came not long after a two-car crash on the SH1 Southern Motorway just before the Mt Wellington Highway off-ramp.
The incident happened shortly after 6.30am and partly blocked the right lane, citybound. No one was injured.
Emergency services cleared the site about 6.45am, but delays had backed up towards Highbrook and drivers were told to expect delays.
SOUTHWESTERN MOTORWAY:
Traffic is heavy between Maioro St and Queenstown Rd, southbound.
Northbound, the earlier crash on Māngere Bridge is causing delays backing towards the Southern Link.
Those heading through the Waterview Tunnel, northbound, will be happy to know traffic is flowing.
NORTHERN MOTORWAY:
Traffic heading northbound is free flowing, the NZTA said, while traffic going towards the city is heavy between Greville Rd and Onewa Rd.
NORTHWESTERN MOTORWAY:
Motorists travelling from West Auckland into the city can expect heavy congestion between Hobsonville Rd and Royal Rd.
Traffic between Rosebank Rd to St Lukes is moderate to heavy.
Westbound traffic is free flowing, while traffic through the Waterview Tunnel, southbound, is also fine.
Traffic is expected to be heavy this morning as most students head back to school today.
Meanwhile, Ohura Rd in Strathmore, near Stratford, has been closed after a logging truck rolled there about 5.30am.
The blockage is about 5km north of the Strathmore Saddle. Delays are expected in the area and motorists are being told to avoid the road if possible.
No one was injured in the incident.