I have come across many people who were drunk when driving. Unfortunately a good number of them have been truck drivers which is really scary. Now drunk or stoned I have no idea.
When i was working as an Environmental regulator I had a radio in my car and so I could contact the nearest State police station. I always made sure I was right by watching them so a good while before I passed them and they saw I was a Fed or State employee. they usually slowed down then but it was also too late.
BTW where I worked it was legal for authorized state employees to call in possible DUI drivers.
"Those who do not learn from history and condemned to relive it".
"There are those who will debate the necessity of wilderness, I will not, either you know it in your bones or you are very very old". Aldo Leopold - Sand County Almanac