The ramp was designed to generate exceptional speed at the start of a run to allow a rider to cover the track and its various jumps as quickly as possible, Coroner Shortland said in his findings.
Dion's mother never saw him descend the ramp and later found him over the first jump lying at an unusual angle to his bike.
Medical evidence stated that Dion had gone into cardiac arrest following his crash and was rendered unconscious.
CPR was performed on him at the scene of the accident and a mechanical ventilation machine took over when he arrived at hospital.
Tragically, Dion had suffered a serious spinal injury which left him in the opinion of spinal surgeons with little realistic possibility of any significant improvement, including the inability to breathe by himself, the finding stated.
Coroner Shortland said it was clear that the spinal cord injury was totally devastating. "There was no prospect of meaningful or significant recovery.''
The tragedy could only be described as "an absolute chance accident'', he said.
"Dion had been to the track previously with his mother. He was a conscientious and responsible rider.
"He was confident enough that he started his run at the top of the ramp and knew the track to a certain extent. After launching from jump one he has landed awkwardly over jump two and crashed his bike, leaving him with injuries that became unsurvivable.
"It is an unfortunate and preventable death, nevertheless, it is not unexpected given the intensity, and potential danger BMX riding offers. It was a pure accident and it could happen to any rider at any time.''
Coroner Shortland said he was satisfied Dion did not ride beyond his abilities. "In fact, he was confident and competent enough to engage the course.''
