Mr Knight said police suspected the man, who had not been named yesterday, was not wearing his seatbelt and as a result was thrown from the cab which he said rolled over and crushed him.
A passing motorist found the two-trailer truck on its side on SH27 in the Mangatarata area, 90km southeast of Auckland.
The truck and trailer unit blocked both lanes of the road and diversions lasting until 10am yesterday were put in place.
Mr Knight said heavy haulage equipment including a crane was needed to clear the road, which was littered with broken bottles, boxes of beer, spirits and trays of eggs.
"It was a bloody mess," he said.
In an earlier interview with the Herald, Waikato road policing manager Leo Tooman said police were still attending a number of fatal accidents involving motorists not wearing seatbelts.
He told other media yesterday that the man would probably be alive if he had worn one.
The Waikato serious crash unit is investigating the crash and the matter has been referred to the coroner.
The Waikato road toll stands at 35 this year, four more than at the same time a year ago.
The fatal crash was one in a number of traffic incidents between Monday afternoon and yesterday.
A log truck driver escaped unharmed after his truck flipped between Gisborne and Wairoa at the top of the Wharerata Hills at about 4.15pm on Monday. The truck and trailer clipped a rail bridge which caused it to overturn, spilling around 45 tonnes of logs across the road.
Meanwhile, SH2 was closed and traffic diverted when two trucks crashed southeast of Mt Maunganui, about 7.30am yesterday.
SH 29 also saw four separate incidents in less than one hour with police blaming fog for causing an oil spill and three separate nose-to-tail crashes in the Lower Kaimai ranges between Matamata and Tauranga.
