State Highway 20 is closed westbound between the Redoubt Road onramp and the Lambie Drive offramp following an earlier crash.
SH20 links from State Highway 1 are also impacted.
There are closures northbound at Great South Road and southbound at Redoubt Road.
The crash, involving a motorcyclist, was reported to Police at 1.11pm. One person sustained critical injuries.
Motorists are advised to expect delays and seek alternative routes.
The Serious Crash Unit is in attendance.
ENDS.
Frankie Le Roy/NZ Police.