Road freight operators say safety improvement work on State Highway 5 between Taupō and Napier cannot start soon enough.
The NZ Transport Agency Waka Kotahi project manager Chris Mahoney told RNZ that 60 serious crashes and 13 deaths had occurred along the stretch in the seven years prior to 2023.
On Monday, contractors begin work widening centrelines and shoulders, and installing safety barriers at high-risk bends.
Crews will also continue repairing potholes and resealing and re-marking parts of the road's surface
Transporting New Zealand interim chief executive Dom Kalasih said the difficult geography of the area meant the work would have a far greater safety benefit than blanket speed reductions.
"On the north end, there's quite a long section of road where it was relatively straight and the speed was reduced, now that's unlikely to make that much difference.
"Whereas the type of work they're doing now - cordon widening, shoulder widening, centre line widening - in a really demanding piece of the network, that is where the risk is."
Kalasih said that part of SH5 had had a bad history of crashes.
"Trucks do try to pull over where they can, but often a lot of our slow vehicle bays... are still pretty marginal... They're still very narrow, very short.
"These changes will make it easier for other motorists to get past the trucks."
Kalasih said any costs incurred because of delays during the construction would be well justified, and he hoped motorists would be patient while the work was underway.