Driver error blamed for death of driver
But Australian motorsport officials have moved to modify the Adelaide street circuit where Cooper slammed into a concrete barrier at high speed in February.
Confederation of Australian Motor Sport (CAMS) chief executive Graham Fountain said on the investigation had confirmed that the track, Cooper's car, his safety equipment and the conditions on the day did not contribute to the cause of the 27-year-old's crash.
"Unfortunately, it was a mistake, we're all humans and we all make mistakes," Fountain said.
"Ashley was a very experienced driver and unfortunately there was a mistake that led to the accident.
"This mistake resulted in Ashley's unfortunate death. It was a misjudgment."
Cooper, from Ulladulla in New South Wales, died in hospital from severe head injuries after crashing his VZ Commodore into the barriers on the exit of turn eight, the fastest on the Adelaide circuit.
He was competing in the Fujitsu V8 Supercar Series, a development program for the main V8 Supercar series.
The sweeping right hander that claimed his life has been the subject of controversy for several years and is often the scene of major incidents during the Clipsal 500 carnival.
Changes have been made a number of times, including the introduction and later removal of a chicane.
Under the latest changes, an extra race line barrier will be installed in 2009 to change the alignment of the corner and to narrow the track at that point.