Key Points:

A West Coast mother who mounted a search for her son when he didn't arrive home found him 57km away, trapped and injured in his car.

Danny Milne, 39, did not arrive home in Kumara on Sunday after a trip to Christchurch.

After driving about 100km between Kumara and Arthurs Pass she spotted skid marks at Rocky Point, west of Otira. "I screamed out to [the driver] to stop and jumped out of the car and started screaming," she said. "Danny must have heard me and started banging on the car."

Mr Milne had been trapped upside down in his car all night on the edge of a cliff. He was flown to Greymouth Hospital where he is being treated for a broken hip and broken ribs.