A man was seriously injured when his car rolled backwards down a New Plymouth driveway and flipped.

St John Ambulance spokeswoman Victoria Hawkins said the 57-year-old man had been trapped under the car and was taken to Taranaki Base Hospital in serious condition.

Alistair, who lives next door to the man, said he heard a "big crash and a bang".

"I came out and looked down and saw him on his roof down the driveway, so went down and his feet were stuck in the door.

Advertisement

"I think he went to hop out of his car at the top of the hill and he had no handbrake on so as soon as he took his foot off the brake the car got away from him and he had his feet still out the door."

Alistair said the car rolled up to 4m and flipped after hitting a bank on the side of the driveway.

A police spokesperson said they believed the man was injured when he tried to stop the car rolling.

Emergency services were called Lorna St in Lynmouth about 10am.

The police spokesperson said fire services have set up traffic diversions.