We were promised urgent improvements to the stretch of SH1 between Manakau and Levin (see A possibly slightly safer road to Levin before Christmas 2018), and indeed these have now been implemented.
Along some stretches of road flexible median posts have been installed, as you can see by zooming in on this photo taken at the corner of Waikawa Beach Road and SH1.

There are also a couple of new very prominent signs advising of the high crash rate.

Here’s hoping these will have the desired effect in the short-term.