Less easy to demonstrate impairment in the case of a sleepy driver, certainly.

Unfortunately people in cars are always killing others in cars or themselves whether they are in a rush, inattentive, or outright impaired. Sometimes you hear about it and wonder how the hell it happened but unfortunately bikes are traffic too and so aren't immune to these predations.

Most of the transcanada is lightly travelled, certainly by 401 standards, so there's often no excuse for not moving into a passing lane. In the prairies there's absolutely no excuse. Have driven there a lot, I know how the road can paralyze you after driving straight for an hour or more, but you're rarely pressed for lane space and can see long distances in advance.

I wish I had a magic solution. But I don't so once again my thoughts to the friends and families of these cyclists.