The agency is tightening up on letting motorists cross Porters and Arthur’s Passes (both SH73) this winter.
Previously, if conditions allowed, drivers had been allowed to use the main road between Christchurch and the West Coast when it snowed, as long as they could fit chains.
But this winter, the road would be closed while graders cleared the snow and laid down grit, and vehicles would only be allowed to pass once it was safe.
Agency system manager Pete Connors said the open/closed management regime had been very successful on the Lewis Pass (SH7) and Rahu Saddle near Reefton, since 2017.
‘‘We wanted to extend the same system to the Arthur’s and Porters Passes for everyone’s benefit.
‘‘It is simpler and safer for both road crews and road users in terms of fewer delays and less diversions caused by drivers getting stuck in snow drifts or sliding on ice.’’
However, the regime would not be implemented on Otago’s highest roads - the Lindis Pass (SH78) and the Crown Range, linking Queenstown and Wanaka.
People driving through the Lindis Pass, between Omarama and Cromwell, would be allowed to pass if they carried chains and knew how to fit them quickly.
However, if conditions were very bad, crews would close the highway or restrict road users to non-towing vehicles.
Crown Range Rd, between Wanaka and Queenstown, is managed by the Queenstown Lakes District Council and is open to vehicles with chains.
The council has a daily road update providing advice for people heading to the skifields.
Most highways in Otago and Southland managed by transport agency highway maintenance crews would largely follow the same system as the alpine pass management one - either open or closed, if winter conditions made travel marginal or unsafe.
That included SH1 into Dunedin, from the north, where crews often laid grit or de-icing material ahead of below-zero temperatures.
In some cases, the roads may be open to non-towing vehicles.
The Milford Road (SH94) is managed by the Milford Road Alliance (Downer NZ and the NZ Transport Agency) and is either open or closed.
