Jonathan Pratt's defence lawyer had argued that his client wasn't driving the truck.
But the judge said there wasn't any evidence to suggest that anyone else was at the scene and it would have been "practically impossible" for another person to escape uninjured.
Court heard Pratt was driving nearly 200 km/h when his truck rear-ended the car near Beaumont and virtually demolished it in November 2011.
Pratt, who is 30, was found under his truck and spent six weeks in hospital with a broken leg and head injuries.
Bradley Arsenault and Kole Novak, both 18, and Thaddeus Lake, 22, were inside the car and died.
The trial heard that Pratt was the only other person found at the scene and had a blood alcohol level of about three times the legal limit.