Motorists on one of the country's most scenic highways desperately called police to warn about a vehicle's erratic driving before a fatal crash on Monday.
Monday evening's horror smash on SH8 near Lake Pukaki killed two people, including local Twizel identity Nigel Freeman.
Police received three calls over a 15km stretch of highway from concerned motorists about one of the vehicles involved in the deadly smash.
"It was just the manner of driving to the extent that it caused three other motorists on the road to be concerned with the ability of the driver."
Mid-South Canterbury area commander Inspector Dave Gaskin said police tried to head off the vehicle before anything happened.