A man has suffered serious injuries when he was hit by a vehicle while walking next to the road in the northbound lane on SH2, between North Street and Ahikōuka Road, Greytown.
The man was left at the scene.
The incident took place on Sunday 24 June between 6.30am and 7am.
Police said they had tracked a vehicle on CCTV driving through the Greytown area prior to the incident.
It is believed to be a 2016 - 2020 Mitsubishi Triton utility fitted with a flat deck and front bull-bar with side protection.
The driver, who police said may have information that would assist in the investigation, was asked to contact Masterton police as soon as possible.
Anyone in the community who might know the driver, or who owns the vehicle, were also asked to contact police.
Anyone with information can call 105 quoting file number 230625/2031.
Information can also be provided anonymously via Crime Stoppers on 0800 555 111.