A 62-year-old semi-retired farmer, from Mosgiel, was killed while assisting his family on a farm near Lee Stream-Clarks Junction yesterday afternoon.
Emergency services were alerted shortly after 1pm, but the sole occupant of the ute died at the scene, a St John spokeswoman said.
Sergeant Paul McLaughlan, of Dunedin, said the incident was still being investigated, but confirmed speed and alcohol were not factors.
The man's name would not be released until next-of-kin had been notified.
The Department of Labour is investigating.
About an hour earlier, emergency services were called to a collision between a four-wheel-drive vehicle and a Ritchies Intercity bus on State Highway 1 near Orari, about 40km north of Timaru.
The driver of the 4WD, aged 58, died at the scene, and three people on the eight-year-old Volvo bus were taken to Timaru Hospital with moderate injuries.
Next-of-kin were still to be contacted last night and police declined to name the man killed.
Alcohol and speed were not believed to be contributing factors.
Ritchies Intercity regional manager Malcolm Budd said the bus, travelling from Dunedin to Christchurch with 18 passengers, had just left Orari.
The crash happened as the south-bound 4WD passed a campervan that had pulled to the left of the road, Mr Budd said.
The impact sent the bus and the 4WD to the edge of the south-bound lane.
The road was closed for five hours while the serious crash unit, from Christchurch, investigated.
Dunedin-based bus driver Jared Vercoe (26) suffered a lacerated leg but was able to get the passengers safely off the bus, and telephone for help, Mr Budd said.
Mr Vercoe was last night "pretty upset" and recovering with family in Christchurch, Mr Budd said.
He had driven the route for Ritchies and another company for several years.
The passengers, who were taken north on another bus, would be offered counselling.
Dunedin city councillor Jinty MacTavish, a passenger on the bus, said the brakes squealed and passengers lurched forward in the seconds before the collision.
She was sitting near the front and saw the 4WD "a split-second away" from the bus.
There was "no way it was going to miss".
The front of the bus was stove in and the windscreen smashed.
Mr Vercoe directed the dazed and shaken passengers to leave through the rear.
Cr MacTavish helped older women from the bus as the "obviously wounded" Mr Vercoe and two people she believed to be local paramedics did a "fantastic job" helping passengers.
"It's hard to imagine how shocking something like this can be, but the driver and the paramedics did a great job in pretty stressful circumstances."
