The road through the Manawatu Gorge was reopened yesterday afternoon after police recovered the body of a man who died when his truck crashed through barriers and tumbled down a steep bank early yesterday.

The crash is believed to have happened just after midnight when John Douglas Watene, 49, of Feilding, was driving east towards Woodville in a truck and trailer unit.

Police spokeswoman Kim Perks said it appeared Mr Watene lost control of the truck, which came to rest about 15 to 20 metres down the bank. The trailer ended up about 25 metres down the bank, in the Manawatu River.

The busy road that links Palmerston North with Wairarapa and Hawkes Bay was closed twice yesterday, as police waited on specialist lifting equipment and worked to recover Mr Watene's body.

The truck's front unit was lifted from the gorge yesterday afternoon, and the partially submerged trailer will be recovered today.

The road will be closed again at 9 this morning.

"It is a tricky operation so motorists are advised to avoid the area," Ms Perks said.

The serious crash investigation unit is looking into the cause of the crash.

Also early yesterday, in the Waikato, an elderly Whitianga woman was shunted from the road in her car in a hit-and-run police say was "deliberate and terrifying" just hours after another driver collided head-on with an ambulance and fled the scene.

The 66-year-old woman was driving towards the intersection of SH26 and SH27 at Tatuanui, 29km northwest of Matamata, when she was slammed into by another driver, shunting her through a hedge, a fence and then a ditch about 1am.

Waikato police communications manager Andrew McAlley said she was left severely shaken and traumatised.

"There seems to be a degree of deliberateness to this and on top of that she was a 66-year-old woman driving by herself ... It would have been a terrifying ordeal for one of us, let alone an elderly woman."

The hit-and-run followed an earlier incident, also near Matamata, when a driver collided with an ambulance rushing a patient with serious head injuries to Waikato Hospital.

The crash happened on Hinuera Rd, 5km south of Matamata, just after 5pm on Tuesday when a ute appeared to lose control on a bend and crossed the centre line, striking the ambulance's left side. It then continued towards Matamata without stopping.

Sergeant Neil Mansill of the Matamata-Piako strategic traffic unit said the dark-green- or blue-coloured ute suffered damage to the front of its cab.

He said the vehicle would be distinctive, with bull bars on the front hanging down following the crash, and a missing headlight.

Mr Mansill asked people in the wider Waikato to keep an eye out for it.

"Our advice to the driver is that he or she should turn themselves in rather than having to face more serious consequences should police have to locate them."