Ontario Provincial Police are warning people to take traffic seriously after one man was killed and another injured after being struck while changing a flat tire on the Highway 400 on Sunday.

Ontario Provincial Police say at about 6 p.m., a truck driver with a flat tire pulled to the side of the highway, just south of Highway 89 in Innisfil, about 80 kilometres north of Toronto.

The truck driver called his company, which sent a pick-up truck to help fix the tire. Both men were outside on the shoulder of the highway when they were struck by another vehicle.

A 43-year-old man, who had come to assist the driver, was pronounced dead at the scene. The driver was taken to Southlake Regional Health Centre in Newmarket and is expected to recover.

Police say they will not be laying charges.

OPP Sgt. Dave Woodford said drivers should call 911 when the need assistance on the highway, because it is too dangerous to do it alone.

He said emergency crews should be on scene in order to ensure oncoming drivers have proper warning.

"We tell people time and time again: Stay in your vehicle if you break down, call for assistance and don't be out wandering around on the highway," Woodford said. "It is too dangerous out here."