[cripplecreek]

Here in the snowy States we have gates they can lower to prevent access onto the freeways. I think you probably have them, too.

Not that I've ever seen. I'm guessing its a means of keeping people off the highways during snowstorms or something. I agree that enforcing a highway closure for any length of time would be impossible. I-94 just north of me carries thousands of cars and many hundreds of trucks per hour. Any attempt to block it would result in a traffic jam stretching from Detroit to Chicago with thousands of enraged citizens.

[CodeToad]

These are the gates at all entrances to freeways in Colorado and Wyoming.