It is unclear how the vehicle, a Toyota Rav 4, came to hit the pole, on the corner of Cockerell St and Brockville Rd, about 6.45pm.
Witnesses said the man was bleeding "profusely'' from his head, and when they tried to help, became violent.
Sam Sinclair, of Brockville, said he and two other men assisted in restraining the driver, after one had tried to take the driver's keys when he attempted to drive away.
"He was extremely agitated,'' Mr Sinclair said.
"He was determined to knee me.
"I felt uneasy when I was holding him but I wasn't prepared to let him go.''
Mr Sinclair said he was concerned that if he drove off again, he could have seriously injured someone else.
Mr Sinclair's wife, Coralie Abbott, said the driver's actions could have been as a result of hitting his head.
"They got him out of the car and he started swearing.
"He was abusive, he was threatening. He wanted to just get in the car and keep going,'' she said.
"I was relieved that nobody was badly hurt [and] he didn't take out anyone else.''
Another resident who assisted in holding the man down, Tom Gordon, said he "was quite an aggravated chap''.
"He lashed out at the guy who was applying pressure to his head [wound],'' Mr Gordon said.
Senior Sergeant Shona Low, of Dunedin, said police escorted the man in an ambulance to Dunedin Hospital.
"Some members of the public did assist us with [the incident] before police got there.''
Snr Sgt Low said she believed the man had been trying to leave the scene but could not confirm how the accident happened.
She was unable to say whether the driver might have been intoxicated.
No other vehicle was involved.
