Speed limits of between 30km/h and 100km/h will be introduced around the Waterview Tunnel from around April next year.
The news comes as the NZ Transport Agency reveals there were more than 330 incidents including 20 crashes between the opening of the tunnel on July 2 and November 23.
NZTA spokeswoman Kathryn Musgrave said they had been monitoring driver behaviour and operational performance since the opening.
Being able to vary the speed limit will improve traffic flow and the performance of the state highway network. The limit will change depending on the driving conditions and traffic volumes.
The variable speed limits will apply on SH16 between St Lukes and Rosebank Rd and on SH20 between Maioro St and Dominion Rd. The speed limit now is 80km/h in these areas, Musgrave said.
"For most of the day, the maximum speed is likely to be 100km/h, but both sections of SH16 and 20 are very busy during peak periods. Reducing the speed limit during busy periods improves traffic flows, meaning everyone can have a more consistent and safer journey."
Speed limits on the approaches to and inside the Waterview tunnel will not change. The speed limit is set at 80km/h to manage the higher risks associated with a tunnel.
Of the 331 incidents in the tunnel area, only 20 were crashes, all minor, and none was in the tunnel. Almost 60 drivers ran out of fuel, there were 49 flat tyres and 42 breakdowns. A truck that ran out of fuel in the centre lane of the southbound tunnel had to be towed from the tunnel, causing delays of up to 30 minutes for other motorists.
The NZTA urged motorists to avoid the middle lane if the vehicle was running out of fuel.
73 debris picked up
49 flat tyres
59 out of fuel
5 flat batteries
2 car fires
78 Miscellaneous (vehicles have stopped but moved off without assistance)