Waikato police say they're keen to hear from any hunters who were "spotlighting" in the area from where Hamilton man Rick Hayward went missing four years ago.

Detective Sergeant Andrew Saunders fronted to media at the Hamilton Central Police Station this morning.

He said police were now treating Hayward's disappearance as a hit-and-run - although it may not have been deliberate.

However, he wouldn't answer questions around why police believe he was hit by a car and his body possibly disposed of.

Hayward, a married father of two, was last seen leaving his home in Thames St, Hamilton, around 5pm on September 2.

He was meant to be travelling to Raglan. But his red Toyota was found parked at the summit of Old Mountain Rd between Raglan and Hamilton the next day, with his mobile phone inside.

Land Search and Rescue teams and the Police Eagle helicopter spent days combing bush and farmland in the area with no luck.

But after four years police now hope to bring closure to Hayward's wife and children.

"We are not suggesting the driver deliberately hit Rick but in doing so has panicked and disposed of the body.

"The key focus is to find Rick and we are appealing for information on vehicles using Old Mountain Rd and any people or vehicles spotlighting in the area during that period and any vehicles that may have sustained damage."

Spotlighting is where hunters put spotlights on top of their vehicles so they can hunt at night.

Saunders said the road wasn't overly busy, however caution was needed when using it.

"If you go up there you will see, particularly when you get onto the dirt road, you have got to be very careful with your driving. If you travel too fast or slightly dangerously you could quite easily hit someone walking."

Police first released the new lead on Police Ten 7 last night.

"This has been a difficult time for the family of Mr Hayward," Saunders said.

He said it was unlikely that the driver had kept the accident a secret for four years and someone probably has information that would lead to the case being solved.

They may have seen someone driving dangerously, or a damaged vehicle - or someone may have talked about the accident.

On the programme Hayward's wife Kate recounted her last conversation with her husband.

He had called asking if she wanted to go to the family's bach but she declined, saying she had to work.

When his car was found abandoned, "I knew right away that something terrible had happened. I knew that that conversation ... was our last conversation," she said on tonight's programme.

She begged anyone who knew something to come forward to police.

"I would hope that they would have the courage to speak out. it would mean so much to us."

Anyone who can provide information is asked to call Hamilton Police on 07 858 6200, or contact Crimestoppers anonymously on 0800 555 111.

-NZ Herald