A driver was under the influence of cannabis when he drove into the path of an oncoming truck, causing "total carnage'', a coroner has found.
Robert Perry Watene, 21, died from extensive burns and other injuries, including a severed aorta, at the scene of the crash near Waipu in February 2009.
In a written finding, Coroner Brandt Shortland said Mr Watene had been struggling with mental health issues and was suffering from paranoia. Prior to the accident he had stopped taking his medication and was using cannabis.
On the night before the crash he was stopped by police for excessive speeding and overtaking on the flush median.
The following morning he took his father's Holden Commodore and drove from his parents' home in Whangarei, where he was living, towards Waipu.