On this route, SH1 traffic between Puhoi Rd and Johnstones Hill Tunnels is being detoured in both directions via the newly opened motorway. Speed restrictions are in place.
For those travelling at night, there is set to be stop/go roadworks in the Puhoi area but only minor delays are expected.
Between Manukau and Bombay, southbound traffic is expected to be busy until 6.30pm and again between 8.30am and 4.30pm tomorrow.
The transport agency's real-time traffic dashboard shows it is currently taking 47 minutes to drive from Albany to Manukau via SH1, compared to the usual free-flowing duration of 24 minutes.
The drive from Auckland City to Bombay, via SH1, was estimated to take around 53 minutes at 2.30pm. The route usually takes motorists 30 minutes.
In Waikato and Wellington, there didn't appear to be any heavy congestion on the region's state highways as of 2.30pm, according to the dashboard.
Traffic also appeared to be free-flowing, or close to it, in the Bay or Plenty, Hawke's Bay, Manawatū-Whanganui, Taranaki, Christchurch and Otago areas.
In the Far North, six people have been injured in a serious crash involving two cars at the intersection of State Highway 1 and Clough Rd in Kaitāia.
St John said four of the people injured were in serious condition, while two people had minor injuries.
The crash has closed SH1 between Fairburn Rd and Ruaroa Rd and delays are expected.
Meanwhile, police in Southland warned motorists of icy roads across the district this morning, particularly in Dunedin's hilly suburbs.
Roads were frosty and officers urged motorists to drive to the conditions.
