No one witnessed the crash but two people saw the vehicle before it happened.
"The witnesses observed the ute pull out from a side road in front of them, forcing them to slow down very quickly," Mr Devonport said.
"The witnesses observed the ute cross over the centre line and back into the correct lane as it negotiated a number of bends in the road."
They also saw the ute veer on to the shoulder a number of times before losing sight of it on a bend.
"After coming on to a straight, they came across the crash scene."
Neither Mr Walford nor Mr Rotorangi were wearing seatbelts, and both were flung from the ute.
"...the cabin area inside the Mitsubishi ute was relatively undamaged," Mr Devonport said.
"Therefore, had Mr Walford and Mr Rotorangi been wearing seatbelts at the time of the crash, they would likely have remained inside the vehicle and they may have possibly survived the crash."
Mr Devonport concluded Mr Walford had fallen asleep at the wheel, given his high blood alcohol level, erratic driving and the apparent lack of any evasive action.