McLellan Freight Ltd owner Alex McLellan, of Balclutha, said one of his drivers, Gary Cross, was stopped by a motorist about 2.5km north of Dunedin on State Highway 1 on Thursday about 10.45pm, and told two people were standing on the bumper bar of the refrigerated trailer and holding on to the door handles.
The people ran off when the truck stopped, he said.
"It was an unauthorised taxi service.
"My driver was shocked. It's stupidity of the highest order. Their lives were hugely at risk."
Mr McLellan said the truck's next stop was in Pareora, just south of Timaru.
"Hypothermia would have gotten them in the end and they would have fallen off.
"I hope someone can identify these clowns."
Dunedin Police Commercial Vehicle Investigation Unit Sergeant Andrew Savage said a similar incident occurred several years ago, in which two Dunedin students stood on the drawbar of a trailer being towed by a truck, which stopped in Ashburton.
Sgt Savage asked the driver of the vehicle which stopped the truck in the latest incident to contact Dunedin police.
He also asked drivers to be on the lookout for other people attempting to hitch a ride without the driver's knowledge.
"If anyone sees it happen, call Dunedin police straight away.
"If the truck hadn't stopped, who knows what could have happened? "It's just ludicrous behaviour."
