Emergency services were then called to a crash scene near an inner city motel and transitional housing accommodation near the Napier CBD about 1.20pm on Saturday.
Witnesses described the southbound vehicle veering off Munroe St just after exiting a roundabout at the intersection with Raffles St.
Mongrel Mob members nearby at the time joined other passers-by to help as an injured man lay trapped on the downside driver's side of the vehicle.
A paramedic arrived soon after and climbed into the vehicle from the passenger door on the upward side and assisted the injured man as the fire service was being called to assist in freeing him.
The vehicle hit a fence and post outside the City Close Motel, but did not appear to have struck the building.
Witnesses who saw the crash believed the man may have had a medical event behind the wheel, but police said that was yet to be confirmed.
A Hawke's Bay DHB spokesperson said the man was on Sunday afternoon in a stable condition in Hawke's Bay Hospital.
