A woman who alleges she witnessed an attack on a Perth highway and was rammed in her car when she stopped to help, has questioned the police response.

Maddie contacted 720 ABC Perth to describe what she said was a terrifying experience when driving home on Roe Highway, in Perth's east, last week.

"I saw a car pulled over on the verge, then I saw a woman run from the car into the traffic, and she was quickly followed by a man with no shirt on who proceeded to choke her and punch her and he pulled her phone away from her," she said.

"She then came back to try and get her phone back and was assaulted again.

"A couple of other cars had pulled up by this point. The man menaced the other two cars and they drove off. I stayed put and called triple-0."

Maddie said the woman managed to run away but the man then began to threaten her.

"He came back and tried to get into my car but I had locked the doors," she said.

"Then he punched my side window twice."

Maddie said she then drove off in her car but was followed by the man, who had another man with him in the car.

"My first thought was to drive to Midland Police Station but he sped up, cut in front of me, slammed his brakes on and forced me to stop," she said.

"He got out of the car so I reversed and headed off in a different direction; this happened a couple of times.

"I was on the phone to triple zero the whole time and they were asking if I could get to a public place."

Maddie said she was attempting to drive to Midland police station when the man rammed the side of her car, before turning his car to face hers and again forcing her to stop.

"By that point I was hysterical," she said.

"His mate got out the car and went to get something out of the boot."

At that point Maddie was able to drive away, and made it home safely.

"I was completely hysterical by the time I got home, I was crying and shaking and that was upsetting for my kids and my family. But I was home and OK," she said.

Maddie said she was advised to make an online report about the damage to her car and to visit Midland police station the next day, but said that when she did, the staff refused to take a statement.

"I was there for an hour and for most of that time they were trying to make sense of what had happened," she said.

"I spoke to a policeman who said 'I don't understand why you are trying to report it here, that's a traffic matter'.

"He also said 'it might be a life-changing event for you but for us we see this all the time'.

"[The man on Roe Highway] He was certainly trying to hurt me, if not kill me.

"It just left me wondering what has to happen to a person before the police respond.

"I was a witness to serious assault to a young woman on Roe Highway and I think they have an obligation to follow up a witness statement."

WA police official pledges to investigate 'unacceptable' response

Superintendent Peter De La Motte from WA Police told 720 ABC Perth that he believed the service Maddie received from Midland police station was unacceptable.

But he said police responded swiftly to the multiple triple-0 calls they received that afternoon.

"It prompted an urgent response by police and the job was allocated to a vehicle within a minute of the calls going in," he said.

"A person was locked up within minutes of the job coming through and he is on a process through the courts."

Superintendent De La Motte said he would investigate how Midland police handled Maddie's visit.

"What happened when she attended is unacceptable and the service delivery we provided to her is not something that should have occurred," he said.

"The officer in charge of Midland Police station will be in contact with Maddie very soon and we will work what did actually occur and what we can do better."