Mounties in Canmore say an officer had stopped on the Trans-Canada Highway near Lac des Arts after a pedestrian had been hit and killed by a semi-truck.
The dead man was 30 and from Calgary.
RCMP say the eastbound lane of the highway was closed and the police car had its emergency lights flashing when a car hit the police cruiser.
No one was injured.
Thirty-seven-year-old Josh Edward Johnson of Calgary was arrested and charged with impaired driving, driving over 0.8 and dangerous operation of a vehicle.