drug and driving.

I have a neighbor in Vancouver, He uses drug every day, (it is ok in Vancouver), but he drive every day, he is "drug and driving", How to report to police? or, what I can do? When he use drug at home, he did not drive, after he drive, he did not use drug. Can I call 911 to ask police to arrest him and do blood test?(drug test). How to prove he use drug while driving? If police come to his home, he is not driving. or maybe on the road, when he is driving, police can stop him and do drug test?