Private CCTV footage caught the incident on camera. The still shows the moment before the woman was hit.

She was out for a walk with her husband on a balmy November evening and misjudged the road crossing.

Now a 57-year-old Hamilton woman is in a hospital bed nursing serious injuries after being bowled by a car while crossing a bustling road next to a Hamilton roundabout.

She was carried an estimated 10 metres on the bonnet's edge before being propelled on to the grassy sidestrip.

Phillipa Yalden The busy carriageway where the woman was hit.

It happened so quickly that her husband didn't immediately realise what happened.

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When he did, he rushed to her aid and held her hand as vehicles whizzed along the dual lanes of Ohaupo Road.

PHILLIPA YALDEN/STUFF A woman was struck crossing Ohaupo Rd, Hamilton.

The couple had been out walking about 7pm on Thursday when the woman went to cross the road next to the roundabout at the intersection of Tomin Road, Waikato road policing Sergeant Steve Jones said.

Her husband had already made it across the four lanes, using the bicycle lane entrance.

"She's then stepped off the pedestrian refuge in the middle. At that stage there are two lanes still, and across the lanes, she's been struck by a southbound vehicle," Jones said.

She suffered serious leg injuries and was taken to Waikato Hospital in a critical condition, he said.

Jones said the 43-year-old driver of the vehicle - a blue Subaru Legacy - was uninjured and helping police with inquiries.

At this stage there was no indication speed was a factor, Jones said. The area has a 60kmh speed limit.

"She's either not seen it or mistimed her crossing."

A nearby resident who captured the fleeting crash on his home CCTV cameras, said the woman's husband didn't even realise she had been hit.

"It happened so fast. She was hit up there and carried along by the car, on the side of the car, for about 10 metres."

Those living nearby heard the crash and rushed to help.

One witness, who did not wish to be named, said the woman was lying half in the grasses and half on the road.

A group of people had huddled around her.

"They were holding her hand. Some people had stopped their cars so none of the traffic could come near her.

"I think she was hit at the place where people walk across, carried on the car and came off right in front.

"It didn't look particularly good."

Once the ambulance arrived, the woman was quickly bundled inside and, along with her companion, whisked to hospital, she said.

A St John spokeswoman said the woman was transported in a critical condition.

"It's a very busy piece of road. Apparently there were two accidents in October, but we were away," the bystander said.

"It's not a good idea crossing that road right there, as there are too many places to keep your eye on. There are people coming from all directions."

There was a pedestrian crossing on Ohaupo Road, but it was a fair distance from the roundabout, she said.

"It's a walk either way, but for safety, it's the best way to go."

Jones advised all pedestrians to check the road is clear.

"Take care and check both ways and make use of pedestrian refuges - and in this case she has.

"We will look at whether that pedestrian refuge is in the right place around that intersection."

Police's Serious Crash Unit was investigating.