That included two fatal and 10 serious injuries in the five and a half months of 2018 before the posts were installed.
Wilson said there have been no fatal or serious injury crashes reported to the agency since installation.
"The installation of flexible safety posts and other measures is part of the 'safe system' approach to road safety, where mistakes like crossing the centre line are inevitable but don't have to cost lives or serious injuries," Wilson said.
"Safety improvements to a road and the environment around it can significantly reduce the severity of injury or the likelihood of death, in the event of human error.
"We know that centre line barriers are effective in preventing or reducing head-on crashes.
"The fact that the safe hit posts are being struck shows they are doing their job and alerting drivers to potential danger.
"Every crash, injury and death on our roads is a tragedy for families and the wider community.
"The NZ Transport Agency is committed to reducing crash rates on this section of the highway."
He said the short-term improvements were in addition to the ongoing and long-term programme of work to provide safer, easier and more reliable journeys between Whangārei and Te Hana.
Regional Transport Committee chairman John Bain said any reduction in fatal or serious crashes anywhere in Northland was pleasing.
"The fact of life is that road is one of the most heavily used roads in Northland. For there to be no crashes of significance we are very pleased.
"For the very short period they have been there statistics show they have helped keep drivers think about staying on the correct side of the road. We have to credit the safety poles that have been put in place."
He had also received feedback from a truck driver who said red reflectors on bridges in the region had been a road safety improvement that was working well.
The posts were designed to flex or come off if hit and a number have been dislodged since installation, suggesting some motorists were continuing to cross the centre line.