A young boy is lucky to be alive after riding on a vehicle’s roof basket along a major West Australian freeway, with police questioning a woman.

West Australian police have been speaking to a woman, 36, on Sunday after the four-year-old child was spotted on top of the Holden Captiva on Friday while on the Tonkin Highway between Camillo and Harrisdale.

A mother has spoken to police after being seen driving with her young child on the roof of her car. #9News pic.twitter.com/HgNiRDblsg

— 9News Australia (@9NewsAUS) January 5, 2019

Home security vision circulating online shows the child, who is wearing a nappy, sitting on the roof rack as it drove through suburban streets during the ordeal.

Motorists managed to get the attention of the driver who stopped and placed the boy in the car, with two other children inside the vehicle, before driving away.

It is not clear whether the driver knew the child was outside the vehicle.

Police responded after calls came in and found the Holden pulling into a petrol station in Harrisdale where three children, two secured in child restraint seats, were seen in the car.

Officers say the four-year-old boy was unrestrained.

-AAP