A man who crashed a truck has not been charged with causing the death of a 4-year-old passenger.

The accident occured in January when Ross William Smaill drove his unlicenced truck off the highway near Edendale, while trying to let other vehicles pass.

The 12-tonne truck rolled down a grass bank, through a fence and came to rest on its side.

One of the passengers - a 4-year-old boy - later died in an ambulance.

The defendant was not charged with causing the fatality because the cause of death was ruled to be a cardiac arrest.