"He was flooring it - the woman was just driving at a normal pace, he tried to hit the brakes, there was so much tyre smoke it literally engulfed the car," the man said.
"When he hit her she lost all faculties of survival, panicked and went straight into the hedge and hit the pole."
It was not raining at the time, and he described road conditions as "perfect".
"I would say he has done a few thousand dollars worth of damage to the car, but it was more important to make sure the other person was all right."
The witness helped to divert traffic while his neighbour checked on the injured woman and yelled for someone to call an ambulance.
She had been complaining of lower lumbar pain, had a suspected broken nose and was taken to Hawke's Bay Hospital by St John Ambulance.
A hospital spokeswoman said the woman was later discharged.
Another neighbour was getting his children ready for their evening bath when he heard a series of loud noises, then a "bang" before looking out the window in time to see a car in his hedge.
"There was a flash as I walked down the hallway, it must have been the light going out, then I watched as the power pole fell down.
"It was a bit of a surprise for sure, I went outside and a couple of guys from across the road told me to call emergency services."
It was not until he got off the phone that he got a good look at the other vehicle involved.
Police did not respond as to whether the constable had been stood down pending the result of the investigation.
