The car then veered to the left, wiping out 15m of a post and wire fencing before coming to rest.
Senior Sergeant Carolyn Watson said initial inquiries had revealed the car had been heading east "at high speed" when it hit the traffic island.
It's not known whether alcohol was a factor.
She said the driver was trapped, surrounded by live wires "to within a few inches of his head".
He remained like that until emergency services enlisted the help of a lines crew who cut power to the lines and rendered the car safe enough to begin extracting the driver from the wreckage.
Mr Sheeran was taken by ambulance to Wairarapa Hospital where he was admitted to the high dependency unit.
Late yesterday doctors were planning to transfer Mr Sheeran to Wellington Hospital for further specialist care.
His condition was given as serious.