Only places I saw those was in Minnesota and the Dakotas, for controlling access to freeways during blizzards... and places like Chicago and Seattle where they have bi-directional express lanes that switch traffic flow directions based on rush hour needs.
We don't have those around here.
But I hate the trapped feeling when on an interstate and it turns into a parking lot, and all that keeps you there is a stoopid little fence separating you from a farm road or frontage road.
I'm not saying I'd use them routinely... that's why they'd be in the emergency box. For emergencies.
I remember sitting in traffic outside of Baton Rouge for about 2 hours. Took me 2 hours to go maybe 20-25 miles to New Orleans. It was damned hot, and damned muggy, and I was on my bike in full gear, and I had no air flow. There was a fence next to I-10 (this was just west of the Mississippi crossing there) and I was SOOO tempted to whip out my skeletool and cut the fence, and get on the frontage road next to the highway. If it were an emergency, I would have.