There are also temporary "checkpoints" (the real term escapes me at the moment), where police park their cars, funnel traffic to one or two lanes, and ask for I

There are also temporary "checkpoints" (the real term escapes me at the moment), where police park their cars, funnel traffic to one or two lanes, and ask for ID from all cars passing through. I've only ever seen this done at highway on-ramps or major roads on nights notorious for drinking. With those, anybody driving on the road would be stopped, even if they followed every law.