But he said another driver - Sung Jin Kim - followed him, kept tooting and also pulled over.
Hallwright told the court that he got out of his car, opened Mr Kim's door and asked him in a loud voice "What is your problem?"
"There was a look on his face that made me extremely alarmed. He looked menacing ... He had his teeth clenched and he was staring malevolently at me. I think I described it as sort of snarling."
Hallwright went back to his car and tried to leave but Mr Kim appeared at his bonnet.
He said Mr Kim started banging on his bonnet and shouting.
Hallwright said he was waiting for a gap in the traffic to get away.
"There was a split second where he was around the side of the car ... There was a break in the traffic and I thought this was my chance."
He said he could not see Mr Kim when he drove off.
Mr Kim was left with two broken legs and has told the court he needed eight lots of surgery.
Crown prosecutor Ross Burns put a series of questions to Hallwright about what he saw of Kim as he drove off.
He said even if Mr Kim had been towards the side of Hallwright's car as the defence said, he would still be visible: "You couldn't have missed him."
Hallwright said his focus was on the road and he wanted to get away.
"He was in front of the car. I started nudging the car and I expected him to get out of the way."
Mr Burns referred to Hallwright's 111 call made shortly after the incident where he told police that an ambulance was on its way.
Hallwright said he must have heard a siren. Mr Burns replied: "Or, you actually knew that he had been hit and was seriously injured."
Mr Burns also asked him about his choice of words that he used with police, including the phrase "I just drove through him".
Hallwright said he was in shock. "I was trying to grab a word."
The jurors visited the court's basement carpark where Hallwright's black Saab was parked but their discussions cannot be reported.
Later the public gallery was filled with lawyers who came to see two of Auckland's top practitioners make their closing arguments to the jury.
Mr Burns said that even if the jurors accept the defence argument that Mr Kim was at the side of the car, he would still have been visible to Hallwright.
Hallwright's lawyer Paul Davison QC told the court his client "believed the risk to get away was a justifiable one".
He said Mr Kim got caught up in his client's wheel and his injuries were regrettable.
Tomorrow the jurors will hear Judge Raoul Neave sum up the case.