The Greymouth Star understands the accident happened when a 4WD driven by an older man clipped the guardrail of a one-way bridge near Bell Hill and went into the creek below, about 1km past the turnoff to Lake Hochstetter.
The occupants had been on their way home to the Gloriavale Christian Community after attending a craft fair in Greymouth.
An off-duty Greymouth firefighter discovered the scene and called emergency services about 3.30pm.
Ngahere Volunteer Fire Brigade fire chief Tommy Daly commended the man's actions: "He did an amazing job to calm all the patients and had the scene under control, ready for the emergency services."
The injured man had somehow got himself out of the vehicle and on to the bank and his condition "took some stabilising".
"It was a careful, drawn-out process - we couldn't move him until the ambulance got there."
A man and woman, understood to be father and daughter, were also injured.
A fire crew from Greymouth, two ambulances and police also attended.
"Everybody worked in together and got it done calmly and with the patients' well-being first."
The Roa Mining West Coast Rescue Helicopter landed in a nearby paddock but bad alpine weather meant the patient was flown to Nelson Hospital instead. From there he was transferred to Wellington on a medical flight.
The road was closed overnight while the serious crash unit investigated.
Greymouth police said they were looking into the cause of the crash.
- By Meg Fulford
