Shane Mahuta was driving on Auckland's southern motorway when he saw a truck in front of him swerve into the median barrier.

It was an overcast January afternoon and the highway, one of the busiest stretches of the Auckland motorway, was greasy from rain.

The driver of the swerving truck, about 500m in front of Mahuta, had had a fatal heart attack.

It was obvious something was wrong and Mahuta, in his fully laden Kuehne and Nagel truck, sped up and overtook the truck on the inside lane.

As he drove past, he saw Anne Dromgool holding the steering wheel from the truck's passenger seat, her arm stretched over the driver's slumped, lifeless body.

She somehow managed to indicate and manoeuvre the truck across to the middle lane.

The truck began to slow to about 50km/h as Mahuta accelerated ahead.

He then gingerly positioned his 38-tonne rig in front of the other truck and began to slow down.

After the two trucks - each about 16m long - made contact, Mahuta gradually applied the brakes and brought them to a halt over a 3.3km straight stretch of the highway.

Police awarded both Mahuta and Dromgool with special commendations, saying their actions prevented a disaster that could have cost lives.

Mahuta said in 13 years of truck-driving experience, nothing could have prepared him for using his own vehicle as a makeshift brake.

But it didn't seem to faze him. After his heroics, he finished work, headed home and was back at work the next morning.