Levin police Senior Sergeant Sam Gilpin said the pedestrian had been identified, but his name was not being released as next-of-kin were still being notified.
It was not known whether speed was a factor.
"We can't really comment about driving manner at this stage," Gilpin said.
Both lanes of SH1 were closed with diversions in place at Kimberley Rd, SH57 and Tararua Rd.
The Serious Crash Unit was carrying out preliminary investigations.
Meanwhile, a motorist was moderately injured when a car rolled in Auckland early this morning.
A police spokeswoman said the crash happened in the suburb of Mt Roskill around 5.20am.
