Southern Motorway closure next weekend

Traffic congestion on the Southern Motorway./File

Part of Auckland's Southern Motorway will close for 12 hours next weekend.

NZ Transport Agency plans to close all southbound lanes between Manukau and Takanini from 8pm Saturday to 8am Sunday.

The lanes would be closed to allow for work to connect a new section of the Papakura Stream Bridge to an existing off-ramp.

Detours would be in place, but the transport agency said delays were likely along the alternative routes and motorists should allow extra time for journeys.

The closure would affect anyone heading home along the motorway after Bonnie Raitt and Six6o concerts in the city on Saturday night.

Transport Agency spokesman Brett Gliddon said the closure was necessary to complete the intended work.

"The concrete takes about 12 hours to set and strengthen and any vibrations from passing traffic can affect this process, which is why we need to keep traffic away from this area," he said.

SH1 traffic would be diverted along Great South Rd, and SH20 traffic heading northbound must take Cavendish Drive.

Motorists travelling southbound on SH20 were to be diverted onto Roscommon Rd, Mahia Rd and Great South Rd.

Citybound lanes would remain open, NZ Transport Agency said.

The connection was part of the $268 million Southern Corridor project intended to create extra lanes and ease traffic congestion.