Tragedy has struck again on Alberta highways, this time Bonnyville RCMP are investigating a crash that killed four people last night including two teens.

It's the latest in a disturbing new trend where drugs or alcohol may be involved.

Within the last few days two young Calgary women were killed in Washington State. State Troopers suspect the driver was under the influence of drugs.

A 37 year old man was also killed in a hit and run crash late Wednesday night at Richmond Road and Sarcee Trail Southwest. Police say alcohol was a factor.

In rural areas, there have been 28 fatal collisions so far in July, five may be alcohol or drug related, including one in southern Alberta near Glenwood. Five people were killed, including three children. Mounties suspect the driver was drunk.

Police are concerned and say Alberta shouldn't have any deaths on highways involving alcohol.

RCMP say impaired driving kills more people than any other criminal code offense, but say some people chose to ignore it.