Coroner McElrea said Mr Bowman remained trapped for about an hour before being found by Zane Doyle, Jireh Hewlett and Tim Marshall as they drove home from an eeling trip.
The three teenagers rolled the car off the trapped man and offered to take him to hospital.
He insisted they didn't call an ambulance, telling them to take him home as he lived "just around the corner".
They placed him on the back seat with his legs out the window and drove him home.
However, when they got there they found he could not stand and one of them called emergency services.
Mr Bowman died two hours after arriving at Timaru Hospital.
His blood alcohol level was 132 milligrams for every 100 millilitres of blood - 52mg above the legal alcohol limit.
Coroner McElrea said Mr Bowman's death was the result of driving while intoxicated and making a bad decision to stop his van without putting on its handbrake.
He had sustained a pelvic fracture and a chest wall injury and was bleeding internally when he was found by the three Mr Doyle, Mr Hewlett and Mr Marshall, Coroner McElrea said.
"The actions of the three young men in stopping at the scene to check that everything was 'all right' and their subsequent actions in rendering assistance to Mr Bowman were exemplary and are to be commended."
